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	$65.91	8.128%	$71.2672	$71.27	$71.25	$71.30
Purchase #2	$39.35	8.172%	$42.5657	$42.57	$42.55	$42.60
Purchase #3	$161.90	11.512%	$180.5379	$180.54	$180.55	$180.50
Purchase #4	$207.95	8.176%	$224.952	$224.95	$224.95	$225.00
Purchase #5	$146.38	8.385%	$158.654	$158.65	$158.65	$158.70
Purchase #6	$68.60	9.165%	$74.8872	$74.89	$74.90	$74.90
Purchase #7	$233.56	13.148%	$264.2685	$264.27	$264.25	$264.30
7 purchase totals =	$923.65		$1,017.1325	$1,017.14	$1,017.10	$1,017.30