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	$225.47	7.470%	$242.3126	$242.31	$242.30	$242.30
Purchase #2	$190.95	7.308%	$204.9046	$204.90	$204.90	$204.90
Purchase #3	$134.98	12.784%	$152.2358	$152.24	$152.25	$152.20
Purchase #4	$120.89	9.173%	$131.9792	$131.98	$132.00	$132.00
Purchase #5	$153.78	8.753%	$167.2404	$167.24	$167.25	$167.20
Purchase #6	$91.35	13.387%	$103.579	$103.58	$103.60	$103.60
Purchase #7	$132.30	8.816%	$143.9636	$143.96	$143.95	$144.00
7 purchase totals =	$1,049.72		$1,146.2152	$1,146.21	$1,146.25	$1,146.20