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	$82.86	13.183%	$93.7834	$93.78	$93.80	$93.80
Purchase #2	$249.98	3.832%	$259.5592	$259.56	$259.55	$259.60
Purchase #3	$80.99	9.550%	$88.7245	$88.72	$88.70	$88.70
Purchase #4	$247.89	6.456%	$263.8938	$263.89	$263.90	$263.90
Purchase #5	$240.59	3.705%	$249.5039	$249.50	$249.50	$249.50
Purchase #6	$191.34	9.418%	$209.3604	$209.36	$209.35	$209.40
Purchase #7	$40.87	11.680%	$45.6436	$45.64	$45.65	$45.60
7 purchase totals =	$1,134.52		$1,210.4688	$1,210.45	$1,210.45	$1,210.50