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	$203.88	7.864%	$219.9131	$219.91	$219.90	$219.90
Purchase #2	$193.78	11.267%	$215.6132	$215.61	$215.60	$215.60
Purchase #3	$132.55	11.446%	$147.7217	$147.72	$147.70	$147.70
Purchase #4	$158.97	3.519%	$164.5642	$164.56	$164.55	$164.60
Purchase #5	$224.41	11.726%	$250.7243	$250.72	$250.70	$250.70
Purchase #6	$85.74	4.726%	$89.7921	$89.79	$89.80	$89.80
Purchase #7	$140.58	3.473%	$145.4623	$145.46	$145.45	$145.50
7 purchase totals =	$1,139.91		$1,233.7909	$1,233.77	$1,233.70	$1,233.80