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	$177.47	7.331%	$190.4803	$190.48	$190.50	$190.50
Purchase #2	$250.81	3.210%	$258.861	$258.86	$258.85	$258.90
Purchase #3	$214.89	12.376%	$241.4848	$241.48	$241.50	$241.50
Purchase #4	$45.26	4.692%	$47.3836	$47.38	$47.40	$47.40
Purchase #5	$222.59	3.169%	$229.6439	$229.64	$229.65	$229.60
Purchase #6	$39.37	7.170%	$42.1928	$42.19	$42.20	$42.20
Purchase #7	$131.55	10.108%	$144.8471	$144.85	$144.85	$144.80
7 purchase totals =	$1,081.94		$1,154.8935	$1,154.88	$1,154.95	$1,154.90