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	$31.27	7.120%	$33.4964	$33.50	$33.50	$33.50
Purchase #2	$87.46	9.298%	$95.592	$95.59	$95.60	$95.60
Purchase #3	$243.74	8.362%	$264.1215	$264.12	$264.10	$264.10
Purchase #4	$248.93	6.510%	$265.1353	$265.14	$265.15	$265.10
Purchase #5	$95.85	8.716%	$104.2043	$104.20	$104.20	$104.20
Purchase #6	$143.70	5.591%	$151.7343	$151.73	$151.75	$151.70
Purchase #7	$222.77	8.840%	$242.4629	$242.46	$242.45	$242.50
7 purchase totals =	$1,073.72		$1,156.7467	$1,156.74	$1,156.75	$1,156.70