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	$65.77	9.425%	$71.9688	$71.97	$71.95	$72.00
Purchase #2	$128.70	3.463%	$133.1569	$133.16	$133.15	$133.20
Purchase #3	$105.52	10.238%	$116.3231	$116.32	$116.30	$116.30
Purchase #4	$119.54	6.781%	$127.646	$127.65	$127.65	$127.60
Purchase #5	$231.89	9.481%	$253.8755	$253.88	$253.90	$253.90
Purchase #6	$90.41	7.230%	$96.9466	$96.95	$96.95	$96.90
Purchase #7	$22.62	12.500%	$25.4475	$25.45	$25.45	$25.40
7 purchase totals =	$764.45		$825.3644	$825.38	$825.35	$825.30