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	$215.49	4.410%	$224.9931	$224.99	$225.00	$225.00
Purchase #2	$93.54	9.761%	$102.6704	$102.67	$102.65	$102.70
Purchase #3	$168.86	12.721%	$190.3407	$190.34	$190.35	$190.30
Purchase #4	$216.84	6.661%	$231.2837	$231.28	$231.30	$231.30
Purchase #5	$191.82	9.403%	$209.8568	$209.86	$209.85	$209.90
Purchase #6	$35.71	11.647%	$39.8691	$39.87	$39.85	$39.90
Purchase #7	$12.59	5.392%	$13.2689	$13.27	$13.25	$13.30
7 purchase totals =	$934.85		$1,012.2827	$1,012.28	$1,012.25	$1,012.40