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	$198.89	13.573%	$225.8853	$225.89	$225.90	$225.90
Purchase #2	$50.51	6.375%	$53.73	$53.73	$53.75	$53.70
Purchase #3	$60.50	5.834%	$64.0296	$64.03	$64.05	$64.00
Purchase #4	$145.67	4.651%	$152.4451	$152.45	$152.45	$152.40
Purchase #5	$247.81	4.252%	$258.3469	$258.35	$258.35	$258.30
Purchase #6	$16.90	7.575%	$18.1802	$18.18	$18.20	$18.20
Purchase #7	$219.41	8.775%	$238.6632	$238.66	$238.65	$238.70
7 purchase totals =	$939.69		$1,011.2803	$1,011.29	$1,011.35	$1,011.20