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	$198.75	6.870%	$212.4041	$212.40	$212.40	$212.40
Purchase #2	$40.39	7.360%	$43.3627	$43.36	$43.35	$43.40
Purchase #3	$244.84	4.155%	$255.0131	$255.01	$255.00	$255.00
Purchase #4	$13.47	7.687%	$14.5054	$14.51	$14.50	$14.50
Purchase #5	$196.84	9.617%	$215.7701	$215.77	$215.75	$215.80
Purchase #6	$141.26	3.278%	$145.8905	$145.89	$145.90	$145.90
Purchase #7	$203.76	12.506%	$229.2422	$229.24	$229.25	$229.20
7 purchase totals =	$1,039.31		$1,116.1881	$1,116.18	$1,116.15	$1,116.20