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	$204.95	12.171%	$229.8945	$229.89	$229.90	$229.90
Purchase #2	$54.92	11.616%	$61.2995	$61.30	$61.30	$61.30
Purchase #3	$176.56	6.201%	$187.5085	$187.51	$187.50	$187.50
Purchase #4	$201.85	11.636%	$225.3373	$225.34	$225.35	$225.30
Purchase #5	$74.85	11.129%	$83.1801	$83.18	$83.20	$83.20
Purchase #6	$205.71	5.645%	$217.3223	$217.32	$217.30	$217.30
Purchase #7	$140.58	7.263%	$150.7903	$150.79	$150.80	$150.80
7 purchase totals =	$1,059.42		$1,155.3325	$1,155.33	$1,155.35	$1,155.30