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	$200.85	8.702%	$218.328	$218.33	$218.35	$218.30
Purchase #2	$57.92	13.549%	$65.7676	$65.77	$65.75	$65.80
Purchase #3	$167.73	7.537%	$180.3718	$180.37	$180.35	$180.40
Purchase #4	$104.70	7.486%	$112.5378	$112.54	$112.55	$112.50
Purchase #5	$33.94	3.494%	$35.1259	$35.13	$35.15	$35.10
Purchase #6	$77.96	5.785%	$82.47	$82.47	$82.45	$82.50
Purchase #7	$51.80	12.164%	$58.101	$58.10	$58.10	$58.10
7 purchase totals =	$694.90		$752.7021	$752.71	$752.70	$752.70