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	$154.89	11.595%	$172.8495	$172.85	$172.85	$172.80
Purchase #2	$166.39	4.480%	$173.8443	$173.84	$173.85	$173.80
Purchase #3	$93.42	4.369%	$97.5015	$97.50	$97.50	$97.50
Purchase #4	$45.96	5.109%	$48.3081	$48.31	$48.30	$48.30
Purchase #5	$51.32	4.661%	$53.712	$53.71	$53.70	$53.70
Purchase #6	$180.43	12.787%	$203.5016	$203.50	$203.50	$203.50
Purchase #7	$174.50	4.680%	$182.6666	$182.67	$182.65	$182.70
7 purchase totals =	$866.91		$932.3836	$932.38	$932.35	$932.30