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	$146.77	9.405%	$160.5737	$160.57	$160.55	$160.60
Purchase #2	$201.65	5.413%	$212.5653	$212.57	$212.55	$212.60
Purchase #3	$222.32	9.592%	$243.6449	$243.64	$243.65	$243.60
Purchase #4	$74.89	5.355%	$78.9004	$78.90	$78.90	$78.90
Purchase #5	$149.48	11.650%	$166.8944	$166.89	$166.90	$166.90
Purchase #6	$172.77	13.210%	$195.5929	$195.59	$195.60	$195.60
Purchase #7	$120.99	6.149%	$128.4297	$128.43	$128.45	$128.40
7 purchase totals =	$1,088.87		$1,186.6013	$1,186.59	$1,186.60	$1,186.60