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	$226.55	10.864%	$251.1624	$251.16	$251.15	$251.20
Purchase #2	$180.48	8.598%	$195.9977	$196.00	$196.00	$196.00
Purchase #3	$181.49	6.251%	$192.8349	$192.83	$192.85	$192.80
Purchase #4	$133.89	11.191%	$148.8736	$148.87	$148.85	$148.90
Purchase #5	$35.67	10.706%	$39.4888	$39.49	$39.50	$39.50
Purchase #6	$111.77	7.674%	$120.3472	$120.35	$120.35	$120.30
Purchase #7	$90.82	9.448%	$99.4007	$99.40	$99.40	$99.40
7 purchase totals =	$960.67		$1,048.1053	$1,048.10	$1,048.10	$1,048.10