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	$136.52	11.207%	$151.8198	$151.82	$151.80	$151.80
Purchase #2	$167.68	3.813%	$174.0736	$174.07	$174.05	$174.10
Purchase #3	$108.85	8.872%	$118.5072	$118.51	$118.50	$118.50
Purchase #4	$239.37	10.799%	$265.2196	$265.22	$265.20	$265.20
Purchase #5	$108.32	9.761%	$118.8931	$118.89	$118.90	$118.90
Purchase #6	$92.98	11.388%	$103.5686	$103.57	$103.55	$103.60
Purchase #7	$156.47	10.132%	$172.3235	$172.32	$172.30	$172.30
7 purchase totals =	$1,010.19		$1,104.4054	$1,104.40	$1,104.30	$1,104.40