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	$112.84	11.544%	$125.8662	$125.87	$125.85	$125.90
Purchase #2	$173.85	10.339%	$191.8244	$191.82	$191.80	$191.80
Purchase #3	$109.40	4.106%	$113.892	$113.89	$113.90	$113.90
Purchase #4	$151.60	4.525%	$158.4599	$158.46	$158.45	$158.50
Purchase #5	$147.43	3.469%	$152.5443	$152.54	$152.55	$152.50
Purchase #6	$131.49	12.310%	$147.6764	$147.68	$147.70	$147.70
Purchase #7	$209.55	13.862%	$238.5978	$238.60	$238.60	$238.60
7 purchase totals =	$1,036.16		$1,128.8610	$1,128.86	$1,128.85	$1,128.90