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	$179.48	3.472%	$185.7115	$185.71	$185.70	$185.70
Purchase #2	$229.94	13.741%	$261.5361	$261.54	$261.55	$261.50
Purchase #3	$124.92	4.299%	$130.2903	$130.29	$130.30	$130.30
Purchase #4	$147.43	6.152%	$156.4999	$156.50	$156.50	$156.50
Purchase #5	$187.44	9.811%	$205.8297	$205.83	$205.85	$205.80
Purchase #6	$95.53	5.607%	$100.8864	$100.89	$100.90	$100.90
Purchase #7	$134.73	7.128%	$144.3336	$144.33	$144.35	$144.30
7 purchase totals =	$1,099.47		$1,185.0875	$1,185.09	$1,185.15	$1,185.00