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	$155.63	6.368%	$165.5405	$165.54	$165.55	$165.50
Purchase #2	$66.96	6.842%	$71.5414	$71.54	$71.55	$71.50
Purchase #3	$89.44	13.783%	$101.7675	$101.77	$101.75	$101.80
Purchase #4	$96.40	4.324%	$100.5683	$100.57	$100.55	$100.60
Purchase #5	$249.81	6.776%	$266.7371	$266.74	$266.75	$266.70
Purchase #6	$166.93	6.727%	$178.1594	$178.16	$178.15	$178.20
Purchase #7	$139.98	10.119%	$154.1446	$154.14	$154.15	$154.10
7 purchase totals =	$965.15		$1,038.4588	$1,038.46	$1,038.45	$1,038.40