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	$208.78	6.221%	$221.7682	$221.77	$221.75	$221.80
Purchase #2	$206.66	12.371%	$232.2259	$232.23	$232.25	$232.20
Purchase #3	$124.86	3.771%	$129.5685	$129.57	$129.55	$129.60
Purchase #4	$31.75	6.256%	$33.7363	$33.74	$33.75	$33.70
Purchase #5	$101.49	9.463%	$111.094	$111.09	$111.10	$111.10
Purchase #6	$85.69	3.303%	$88.5203	$88.52	$88.50	$88.50
Purchase #7	$229.49	6.374%	$244.1177	$244.12	$244.10	$244.10
7 purchase totals =	$988.72		$1,061.0309	$1,061.04	$1,061.00	$1,061.00