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	$183.76	3.633%	$190.436	$190.44	$190.45	$190.40
Purchase #2	$236.32	9.563%	$258.9193	$258.92	$258.90	$258.90
Purchase #3	$246.73	8.179%	$266.91	$266.91	$266.90	$266.90
Purchase #4	$110.48	12.673%	$124.4811	$124.48	$124.50	$124.50
Purchase #5	$53.41	10.665%	$59.1062	$59.11	$59.10	$59.10
Purchase #6	$85.48	13.869%	$97.3352	$97.34	$97.35	$97.30
Purchase #7	$9.55	9.703%	$10.4766	$10.48	$10.50	$10.50
7 purchase totals =	$925.73		$1,007.6644	$1,007.68	$1,007.70	$1,007.60