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	$184.96	10.113%	$203.665	$203.67	$203.65	$203.70
Purchase #2	$194.66	9.767%	$213.6724	$213.67	$213.65	$213.70
Purchase #3	$50.72	10.171%	$55.8787	$55.88	$55.90	$55.90
Purchase #4	$131.40	12.106%	$147.3073	$147.31	$147.30	$147.30
Purchase #5	$94.98	11.103%	$105.5256	$105.53	$105.55	$105.50
Purchase #6	$243.38	5.221%	$256.0869	$256.09	$256.10	$256.10
Purchase #7	$62.53	4.786%	$65.5227	$65.52	$65.50	$65.50
7 purchase totals =	$962.63		$1,047.6586	$1,047.67	$1,047.65	$1,047.70