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	$143.65	13.873%	$163.5786	$163.58	$163.60	$163.60
Purchase #2	$89.35	10.837%	$99.0329	$99.03	$99.05	$99.00
Purchase #3	$104.57	6.299%	$111.1569	$111.16	$111.15	$111.20
Purchase #4	$136.34	3.633%	$141.2932	$141.29	$141.30	$141.30
Purchase #5	$249.48	6.136%	$264.7881	$264.79	$264.80	$264.80
Purchase #6	$66.91	7.487%	$71.9196	$71.92	$71.90	$71.90
Purchase #7	$175.98	3.437%	$182.0284	$182.03	$182.05	$182.00
7 purchase totals =	$966.28		$1,033.7977	$1,033.80	$1,033.85	$1,033.80