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	$148.42	3.782%	$154.0332	$154.03	$154.05	$154.00
Purchase #2	$172.59	13.536%	$195.9518	$195.95	$195.95	$196.00
Purchase #3	$136.33	13.767%	$155.0986	$155.10	$155.10	$155.10
Purchase #4	$239.94	8.115%	$259.4111	$259.41	$259.40	$259.40
Purchase #5	$90.87	10.488%	$100.4004	$100.40	$100.40	$100.40
Purchase #6	$151.54	12.763%	$170.8811	$170.88	$170.90	$170.90
Purchase #7	$79.71	10.292%	$87.9138	$87.91	$87.90	$87.90
7 purchase totals =	$1,019.40		$1,123.6900	$1,123.68	$1,123.70	$1,123.70