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	$144.62	7.412%	$155.3392	$155.34	$155.35	$155.30
Purchase #2	$157.83	4.300%	$164.6167	$164.62	$164.60	$164.60
Purchase #3	$40.33	8.287%	$43.6721	$43.67	$43.65	$43.70
Purchase #4	$247.77	6.719%	$264.4177	$264.42	$264.40	$264.40
Purchase #5	$185.98	6.307%	$197.7098	$197.71	$197.70	$197.70
Purchase #6	$52.98	12.805%	$59.7641	$59.76	$59.75	$59.80
Purchase #7	$39.38	12.492%	$44.2993	$44.30	$44.30	$44.30
7 purchase totals =	$868.89		$929.8189	$929.82	$929.75	$929.80