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	$175.47	11.872%	$196.3018	$196.30	$196.30	$196.30
Purchase #2	$210.39	11.678%	$234.9593	$234.96	$234.95	$235.00
Purchase #3	$89.72	11.375%	$99.9257	$99.93	$99.95	$99.90
Purchase #4	$192.66	9.607%	$211.1688	$211.17	$211.15	$211.20
Purchase #5	$166.46	7.593%	$179.0993	$179.10	$179.10	$179.10
Purchase #6	$70.26	9.601%	$77.0057	$77.01	$77.00	$77.00
Purchase #7	$239.35	9.233%	$261.4492	$261.45	$261.45	$261.40
7 purchase totals =	$1,144.31		$1,259.9098	$1,259.92	$1,259.90	$1,259.90