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	$42.84	12.718%	$48.2884	$48.29	$48.30	$48.30
Purchase #2	$17.71	5.398%	$18.666	$18.67	$18.65	$18.70
Purchase #3	$79.60	3.820%	$82.6407	$82.64	$82.65	$82.60
Purchase #4	$5.55	6.423%	$5.9065	$5.91	$5.90	$5.90
Purchase #5	$67.36	6.479%	$71.7243	$71.72	$71.70	$71.70
Purchase #6	$196.43	10.826%	$217.6955	$217.70	$217.70	$217.70
Purchase #7	$37.65	7.804%	$40.5882	$40.59	$40.60	$40.60
7 purchase totals =	$447.14		$485.5096	$485.52	$485.50	$485.50