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	$73.61	4.842%	$77.1742	$77.17	$77.15	$77.20
Purchase #2	$219.41	10.621%	$242.7135	$242.71	$242.70	$242.70
Purchase #3	$122.48	7.667%	$131.8705	$131.87	$131.85	$131.90
Purchase #4	$77.42	13.350%	$87.7556	$87.76	$87.75	$87.80
Purchase #5	$127.49	3.142%	$131.4957	$131.50	$131.50	$131.50
Purchase #6	$223.49	5.252%	$235.2277	$235.23	$235.25	$235.20
Purchase #7	$168.96	10.864%	$187.3158	$187.32	$187.30	$187.30
7 purchase totals =	$1,012.86		$1,093.5530	$1,093.56	$1,093.50	$1,093.60