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	$196.81	3.547%	$203.7909	$203.79	$203.80	$203.80
Purchase #2	$226.90	11.613%	$253.2499	$253.25	$253.25	$253.20
Purchase #3	$126.37	6.178%	$134.1771	$134.18	$134.20	$134.20
Purchase #4	$129.94	12.782%	$146.5489	$146.55	$146.55	$146.50
Purchase #5	$69.49	3.640%	$72.0194	$72.02	$72.00	$72.00
Purchase #6	$99.30	12.104%	$111.3193	$111.32	$111.30	$111.30
Purchase #7	$172.73	10.796%	$191.3779	$191.38	$191.40	$191.40
7 purchase totals =	$1,021.54		$1,112.4834	$1,112.49	$1,112.50	$1,112.40