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	$182.77	3.681%	$189.4978	$189.50	$189.50	$189.50
Purchase #2	$165.88	7.665%	$178.5947	$178.59	$178.60	$178.60
Purchase #3	$47.91	11.767%	$53.5476	$53.55	$53.55	$53.50
Purchase #4	$209.61	6.786%	$223.8341	$223.83	$223.85	$223.80
Purchase #5	$177.43	7.601%	$190.9165	$190.92	$190.90	$190.90
Purchase #6	$144.50	3.581%	$149.6745	$149.67	$149.65	$149.70
Purchase #7	$227.32	4.202%	$236.872	$236.87	$236.85	$236.90
7 purchase totals =	$1,155.42		$1,222.9372	$1,222.93	$1,222.90	$1,222.90