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	$150.94	6.591%	$160.8885	$160.89	$160.90	$160.90
Purchase #2	$217.32	12.454%	$244.385	$244.39	$244.40	$244.40
Purchase #3	$145.26	11.825%	$162.437	$162.44	$162.45	$162.40
Purchase #4	$88.39	10.526%	$97.6939	$97.69	$97.70	$97.70
Purchase #5	$217.27	12.273%	$243.9355	$243.94	$243.95	$243.90
Purchase #6	$54.91	5.145%	$57.7351	$57.74	$57.75	$57.70
Purchase #7	$155.43	3.194%	$160.3944	$160.39	$160.40	$160.40
7 purchase totals =	$1,029.52		$1,127.4694	$1,127.48	$1,127.55	$1,127.40