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	$9.53	10.626%	$10.5427	$10.54	$10.55	$10.50
Purchase #2	$100.54	8.686%	$109.2729	$109.27	$109.25	$109.30
Purchase #3	$248.41	13.717%	$282.4844	$282.48	$282.50	$282.50
Purchase #4	$216.80	9.586%	$237.5824	$237.58	$237.60	$237.60
Purchase #5	$219.67	9.363%	$240.2377	$240.24	$240.25	$240.20
Purchase #6	$172.51	7.123%	$184.7979	$184.80	$184.80	$184.80
Purchase #7	$36.41	10.758%	$40.327	$40.33	$40.35	$40.30
7 purchase totals =	$1,003.87		$1,105.2450	$1,105.24	$1,105.30	$1,105.20