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	$237.70	11.441%	$264.8953	$264.90	$264.90	$264.90
Purchase #2	$199.72	13.134%	$225.9512	$225.95	$225.95	$226.00
Purchase #3	$55.49	11.612%	$61.9335	$61.93	$61.95	$61.90
Purchase #4	$38.39	9.686%	$42.1085	$42.11	$42.10	$42.10
Purchase #5	$157.41	5.389%	$165.8928	$165.89	$165.90	$165.90
Purchase #6	$14.98	10.273%	$16.5189	$16.52	$16.50	$16.50
Purchase #7	$236.63	10.411%	$261.2655	$261.27	$261.25	$261.30
7 purchase totals =	$940.32		$1,038.5657	$1,038.57	$1,038.55	$1,038.60