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	$43.96	4.192%	$45.8028	$45.80	$45.80	$45.80
Purchase #2	$222.43	11.346%	$247.6669	$247.67	$247.65	$247.70
Purchase #3	$79.33	7.757%	$85.4836	$85.48	$85.50	$85.50
Purchase #4	$101.72	8.714%	$110.5839	$110.58	$110.60	$110.60
Purchase #5	$178.96	10.821%	$198.3253	$198.33	$198.35	$198.30
Purchase #6	$159.77	8.694%	$173.6604	$173.66	$173.65	$173.70
Purchase #7	$149.34	3.693%	$154.8551	$154.86	$154.85	$154.90
7 purchase totals =	$935.51		$1,016.3780	$1,016.38	$1,016.40	$1,016.50