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	$137.28	13.499%	$155.8114	$155.81	$155.80	$155.80
Purchase #2	$113.46	3.680%	$117.6353	$117.64	$117.65	$117.60
Purchase #3	$75.82	11.202%	$84.3134	$84.31	$84.30	$84.30
Purchase #4	$162.82	5.724%	$172.1398	$172.14	$172.15	$172.10
Purchase #5	$248.40	10.781%	$275.18	$275.18	$275.20	$275.20
Purchase #6	$145.92	4.383%	$152.3157	$152.32	$152.30	$152.30
Purchase #7	$93.73	5.602%	$98.9808	$98.98	$99.00	$99.00
7 purchase totals =	$977.43		$1,056.3764	$1,056.38	$1,056.40	$1,056.30