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	$143.47	13.156%	$162.3449	$162.34	$162.35	$162.30
Purchase #2	$206.59	7.604%	$222.2991	$222.30	$222.30	$222.30
Purchase #3	$18.31	10.268%	$20.1901	$20.19	$20.20	$20.20
Purchase #4	$225.68	5.507%	$238.1082	$238.11	$238.10	$238.10
Purchase #5	$23.34	13.459%	$26.4813	$26.48	$26.50	$26.50
Purchase #6	$85.86	11.268%	$95.5347	$95.53	$95.55	$95.50
Purchase #7	$125.35	12.743%	$141.3234	$141.32	$141.30	$141.30
7 purchase totals =	$828.60		$906.2817	$906.27	$906.30	$906.20