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	$180.48	4.463%	$188.5348	$188.53	$188.55	$188.50
Purchase #2	$211.47	8.252%	$228.9205	$228.92	$228.90	$228.90
Purchase #3	$85.63	6.165%	$90.9091	$90.91	$90.90	$90.90
Purchase #4	$133.52	5.531%	$140.905	$140.91	$140.90	$140.90
Purchase #5	$184.50	5.385%	$194.4353	$194.44	$194.45	$194.40
Purchase #6	$64.73	13.218%	$73.286	$73.29	$73.30	$73.30
Purchase #7	$76.99	10.738%	$85.2572	$85.26	$85.25	$85.30
7 purchase totals =	$937.32		$1,002.2479	$1,002.26	$1,002.25	$1,002.20