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	$190.63	8.329%	$206.5076	$206.51	$206.50	$206.50
Purchase #2	$189.88	3.703%	$196.9113	$196.91	$196.90	$196.90
Purchase #3	$84.58	5.842%	$89.5212	$89.52	$89.50	$89.50
Purchase #4	$92.71	9.764%	$101.7622	$101.76	$101.75	$101.80
Purchase #5	$34.46	11.361%	$38.375	$38.38	$38.40	$38.40
Purchase #6	$69.69	7.355%	$74.8157	$74.82	$74.80	$74.80
Purchase #7	$211.37	9.284%	$230.9936	$230.99	$231.00	$231.00
7 purchase totals =	$873.32		$938.8866	$938.89	$938.85	$938.90