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	$32.31	5.630%	$34.1291	$34.13	$34.15	$34.10
Purchase #2	$76.51	4.136%	$79.6745	$79.67	$79.65	$79.70
Purchase #3	$28.80	8.731%	$31.3145	$31.31	$31.30	$31.30
Purchase #4	$81.55	12.135%	$91.4461	$91.45	$91.45	$91.40
Purchase #5	$59.85	3.281%	$61.8137	$61.81	$61.80	$61.80
Purchase #6	$69.30	3.627%	$71.8135	$71.81	$71.80	$71.80
Purchase #7	$59.31	9.288%	$64.8187	$64.82	$64.80	$64.80
7 purchase totals =	$407.63		$435.0101	$435.00	$434.95	$434.90