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	$87.69	3.618%	$90.8626	$90.86	$90.85	$90.90
Purchase #2	$250.61	12.749%	$282.5603	$282.56	$282.55	$282.60
Purchase #3	$175.27	7.429%	$188.2908	$188.29	$188.30	$188.30
Purchase #4	$194.80	13.826%	$221.733	$221.73	$221.75	$221.70
Purchase #5	$42.68	11.743%	$47.6919	$47.69	$47.70	$47.70
Purchase #6	$72.80	4.175%	$75.8394	$75.84	$75.85	$75.80
Purchase #7	$191.35	13.675%	$217.5171	$217.52	$217.50	$217.50
7 purchase totals =	$1,015.20		$1,124.4951	$1,124.49	$1,124.50	$1,124.50