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	$132.64	9.218%	$144.8668	$144.87	$144.85	$144.90
Purchase #2	$82.74	4.778%	$86.6933	$86.69	$86.70	$86.70
Purchase #3	$249.53	7.171%	$267.4238	$267.42	$267.40	$267.40
Purchase #4	$38.34	4.628%	$40.1144	$40.11	$40.10	$40.10
Purchase #5	$90.83	11.144%	$100.9521	$100.95	$100.95	$101.00
Purchase #6	$53.69	13.704%	$61.0477	$61.05	$61.05	$61.00
Purchase #7	$112.93	10.117%	$124.3551	$124.36	$124.35	$124.40
7 purchase totals =	$760.70		$825.4532	$825.45	$825.40	$825.50