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	$167.32	10.121%	$184.2545	$184.25	$184.25	$184.30
Purchase #2	$88.41	7.300%	$94.8639	$94.86	$94.85	$94.90
Purchase #3	$59.66	5.342%	$62.847	$62.85	$62.85	$62.80
Purchase #4	$156.33	5.685%	$165.2174	$165.22	$165.20	$165.20
Purchase #5	$229.37	5.382%	$241.7147	$241.71	$241.70	$241.70
Purchase #6	$172.71	10.342%	$190.5717	$190.57	$190.55	$190.60
Purchase #7	$30.46	11.304%	$33.9032	$33.90	$33.90	$33.90
7 purchase totals =	$904.26		$973.3724	$973.36	$973.30	$973.40