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	$202.58	13.676%	$230.2848	$230.28	$230.30	$230.30
Purchase #2	$61.41	10.428%	$67.8138	$67.81	$67.80	$67.80
Purchase #3	$139.98	13.379%	$158.7079	$158.71	$158.70	$158.70
Purchase #4	$39.54	6.628%	$42.1607	$42.16	$42.15	$42.20
Purchase #5	$119.86	6.582%	$127.7492	$127.75	$127.75	$127.70
Purchase #6	$171.94	10.436%	$189.8837	$189.88	$189.90	$189.90
Purchase #7	$130.90	10.692%	$144.8958	$144.90	$144.90	$144.90
7 purchase totals =	$866.21		$961.4959	$961.49	$961.50	$961.50