Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$199.76	7.715%	$215.1715	$215.17	$215.15	$215.20
Purchase #2	$153.71	12.719%	$173.2604	$173.26	$173.25	$173.30
Purchase #3	$199.78	11.739%	$223.2322	$223.23	$223.25	$223.20
Purchase #4	$189.33	4.347%	$197.5602	$197.56	$197.55	$197.60
Purchase #5	$142.25	11.273%	$158.2858	$158.29	$158.30	$158.30
Purchase #6	$164.55	4.412%	$171.8099	$171.81	$171.80	$171.80
Purchase #7	$193.93	11.322%	$215.8868	$215.89	$215.90	$215.90
7 purchase totals =	$1,243.31		$1,355.2068	$1,355.21	$1,355.20	$1,355.30