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	$95.52	8.201%	$103.3536	$103.35	$103.35	$103.40
Purchase #2	$123.77	6.168%	$131.4041	$131.40	$131.40	$131.40
Purchase #3	$218.67	9.125%	$238.6236	$238.62	$238.60	$238.60
Purchase #4	$199.98	9.495%	$218.9681	$218.97	$218.95	$219.00
Purchase #5	$83.33	8.228%	$90.1864	$90.19	$90.20	$90.20
Purchase #6	$132.65	11.272%	$147.6023	$147.60	$147.60	$147.60
Purchase #7	$200.67	13.710%	$228.1819	$228.18	$228.20	$228.20
7 purchase totals =	$1,054.59		$1,158.3200	$1,158.31	$1,158.30	$1,158.40