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	$74.34	10.450%	$82.1085	$82.11	$82.10	$82.10
Purchase #2	$98.53	6.405%	$104.8408	$104.84	$104.85	$104.80
Purchase #3	$155.76	8.308%	$168.7005	$168.70	$168.70	$168.70
Purchase #4	$212.70	4.117%	$221.4569	$221.46	$221.45	$221.50
Purchase #5	$60.77	3.241%	$62.7396	$62.74	$62.75	$62.70
Purchase #6	$244.85	13.590%	$278.1251	$278.13	$278.15	$278.10
Purchase #7	$84.37	3.811%	$87.5853	$87.59	$87.60	$87.60
7 purchase totals =	$931.32		$1,005.5567	$1,005.57	$1,005.60	$1,005.50