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	$150.98	9.547%	$165.3941	$165.39	$165.40	$165.40
Purchase #2	$149.29	5.528%	$157.5428	$157.54	$157.55	$157.50
Purchase #3	$144.52	8.560%	$156.8909	$156.89	$156.90	$156.90
Purchase #4	$185.55	6.131%	$196.9261	$196.93	$196.95	$196.90
Purchase #5	$239.93	8.332%	$259.921	$259.92	$259.90	$259.90
Purchase #6	$11.46	3.188%	$11.8253	$11.83	$11.85	$11.80
Purchase #7	$134.66	10.652%	$149.004	$149.00	$149.00	$149.00
7 purchase totals =	$1,016.39		$1,097.5042	$1,097.50	$1,097.55	$1,097.40