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	$182.76	12.434%	$205.4844	$205.48	$205.50	$205.50
Purchase #2	$46.81	7.330%	$50.2412	$50.24	$50.25	$50.20
Purchase #3	$248.50	5.767%	$262.831	$262.83	$262.85	$262.80
Purchase #4	$187.28	3.869%	$194.5259	$194.53	$194.55	$194.50
Purchase #5	$48.69	13.284%	$55.158	$55.16	$55.15	$55.20
Purchase #6	$212.31	12.439%	$238.7192	$238.72	$238.70	$238.70
Purchase #7	$80.61	12.562%	$90.7362	$90.74	$90.75	$90.70
7 purchase totals =	$1,006.96		$1,097.6959	$1,097.70	$1,097.75	$1,097.60