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	$61.45	9.515%	$67.297	$67.30	$67.30	$67.30
Purchase #2	$122.81	3.458%	$127.0568	$127.06	$127.05	$127.10
Purchase #3	$152.53	8.604%	$165.6537	$165.65	$165.65	$165.70
Purchase #4	$40.65	9.495%	$44.5097	$44.51	$44.50	$44.50
Purchase #5	$209.51	11.231%	$233.0401	$233.04	$233.05	$233.00
Purchase #6	$158.51	10.111%	$174.5369	$174.54	$174.55	$174.50
Purchase #7	$73.77	5.846%	$78.0826	$78.08	$78.10	$78.10
7 purchase totals =	$819.23		$890.1768	$890.18	$890.20	$890.20