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	$172.75	5.760%	$182.7004	$182.70	$182.70	$182.70
Purchase #2	$228.80	6.594%	$243.8871	$243.89	$243.90	$243.90
Purchase #3	$167.54	13.575%	$190.2836	$190.28	$190.30	$190.30
Purchase #4	$85.95	7.331%	$92.251	$92.25	$92.25	$92.30
Purchase #5	$190.46	10.588%	$210.6259	$210.63	$210.65	$210.60
Purchase #6	$82.32	7.209%	$88.2544	$88.25	$88.25	$88.30
Purchase #7	$237.41	11.599%	$264.9472	$264.95	$264.95	$264.90
7 purchase totals =	$1,165.23		$1,272.9496	$1,272.95	$1,273.00	$1,273.00