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	$31.42	4.123%	$32.7154	$32.72	$32.70	$32.70
Purchase #2	$13.38	4.317%	$13.9576	$13.96	$13.95	$14.00
Purchase #3	$250.77	9.775%	$275.2828	$275.28	$275.30	$275.30
Purchase #4	$190.69	8.385%	$206.6794	$206.68	$206.70	$206.70
Purchase #5	$229.81	6.372%	$244.4535	$244.45	$244.45	$244.50
Purchase #6	$41.60	10.448%	$45.9464	$45.95	$45.95	$45.90
Purchase #7	$96.94	12.547%	$109.1031	$109.10	$109.10	$109.10
7 purchase totals =	$854.61		$928.1382	$928.14	$928.15	$928.20