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	$140.71	6.776%	$150.2445	$150.24	$150.25	$150.20
Purchase #2	$249.62	7.510%	$268.3665	$268.37	$268.35	$268.40
Purchase #3	$62.68	6.853%	$66.9755	$66.98	$67.00	$67.00
Purchase #4	$242.52	5.782%	$256.5425	$256.54	$256.55	$256.50
Purchase #5	$100.34	11.564%	$111.9433	$111.94	$111.95	$111.90
Purchase #6	$218.98	6.530%	$233.2794	$233.28	$233.30	$233.30
Purchase #7	$243.27	7.165%	$260.7003	$260.70	$260.70	$260.70
7 purchase totals =	$1,258.12		$1,348.0520	$1,348.05	$1,348.10	$1,348.00