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	$196.33	12.573%	$221.0146	$221.01	$221.00	$221.00
Purchase #2	$225.80	13.575%	$256.4524	$256.45	$256.45	$256.50
Purchase #3	$162.96	7.823%	$175.7084	$175.71	$175.70	$175.70
Purchase #4	$81.60	12.118%	$91.4883	$91.49	$91.50	$91.50
Purchase #5	$140.59	7.670%	$151.3733	$151.37	$151.35	$151.40
Purchase #6	$156.88	6.102%	$166.4528	$166.45	$166.45	$166.50
Purchase #7	$122.82	7.223%	$131.6913	$131.69	$131.70	$131.70
7 purchase totals =	$1,086.98		$1,194.1811	$1,194.17	$1,194.15	$1,194.30