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	$74.69	10.717%	$82.6945	$82.69	$82.70	$82.70
Purchase #2	$219.25	7.168%	$234.9658	$234.97	$234.95	$235.00
Purchase #3	$99.51	12.702%	$112.1498	$112.15	$112.15	$112.10
Purchase #4	$237.98	4.663%	$249.077	$249.08	$249.10	$249.10
Purchase #5	$240.95	5.456%	$254.0962	$254.10	$254.10	$254.10
Purchase #6	$37.27	7.464%	$40.0518	$40.05	$40.05	$40.10
Purchase #7	$80.40	9.571%	$88.0951	$88.10	$88.10	$88.10
7 purchase totals =	$990.05		$1,061.1302	$1,061.14	$1,061.15	$1,061.20