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	$160.34	7.702%	$172.6894	$172.69	$172.70	$172.70
Purchase #2	$99.81	12.102%	$111.889	$111.89	$111.90	$111.90
Purchase #3	$129.93	10.719%	$143.8572	$143.86	$143.85	$143.90
Purchase #4	$177.58	11.219%	$197.5027	$197.50	$197.50	$197.50
Purchase #5	$61.74	12.833%	$69.6631	$69.66	$69.65	$69.70
Purchase #6	$180.70	4.440%	$188.7231	$188.72	$188.70	$188.70
Purchase #7	$211.36	5.145%	$222.2345	$222.23	$222.25	$222.20
7 purchase totals =	$1,021.46		$1,106.5590	$1,106.55	$1,106.55	$1,106.60