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	$41.46	3.452%	$42.8912	$42.89	$42.90	$42.90
Purchase #2	$212.84	11.692%	$237.7253	$237.73	$237.75	$237.70
Purchase #3	$166.43	3.639%	$172.4864	$172.49	$172.50	$172.50
Purchase #4	$152.93	6.136%	$162.3138	$162.31	$162.30	$162.30
Purchase #5	$247.72	10.688%	$274.1963	$274.20	$274.20	$274.20
Purchase #6	$177.29	9.597%	$194.3045	$194.30	$194.30	$194.30
Purchase #7	$154.38	11.847%	$172.6694	$172.67	$172.65	$172.70
7 purchase totals =	$1,153.05		$1,256.5869	$1,256.59	$1,256.60	$1,256.60