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	$167.97	13.405%	$190.4864	$190.49	$190.50	$190.50
Purchase #2	$145.29	8.671%	$157.8881	$157.89	$157.90	$157.90
Purchase #3	$55.52	6.819%	$59.3059	$59.31	$59.30	$59.30
Purchase #4	$161.79	7.721%	$174.2818	$174.28	$174.30	$174.30
Purchase #5	$230.34	10.416%	$254.3322	$254.33	$254.35	$254.30
Purchase #6	$153.43	7.750%	$165.3208	$165.32	$165.30	$165.30
Purchase #7	$157.57	12.273%	$176.9086	$176.91	$176.90	$176.90
7 purchase totals =	$1,071.91		$1,178.5238	$1,178.53	$1,178.55	$1,178.50