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	$62.57	7.217%	$67.0857	$67.09	$67.10	$67.10
Purchase #2	$97.76	6.293%	$103.912	$103.91	$103.90	$103.90
Purchase #3	$224.52	10.244%	$247.5198	$247.52	$247.50	$247.50
Purchase #4	$140.31	13.598%	$159.3894	$159.39	$159.40	$159.40
Purchase #5	$45.36	6.687%	$48.3932	$48.39	$48.40	$48.40
Purchase #6	$142.37	10.211%	$156.9074	$156.91	$156.90	$156.90
Purchase #7	$155.37	7.261%	$166.6514	$166.65	$166.65	$166.70
7 purchase totals =	$868.26		$949.8589	$949.86	$949.85	$949.90