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	$63.69	5.167%	$66.9809	$66.98	$67.00	$67.00
Purchase #2	$80.88	11.207%	$89.9442	$89.94	$89.95	$89.90
Purchase #3	$26.66	3.208%	$27.5153	$27.52	$27.50	$27.50
Purchase #4	$236.58	11.245%	$263.1834	$263.18	$263.20	$263.20
Purchase #5	$219.63	9.827%	$241.213	$241.21	$241.20	$241.20
Purchase #6	$232.89	5.762%	$246.3091	$246.31	$246.30	$246.30
Purchase #7	$143.63	11.762%	$160.5238	$160.52	$160.50	$160.50
7 purchase totals =	$1,003.96		$1,095.6697	$1,095.66	$1,095.65	$1,095.60