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	$239.45	10.320%	$264.1612	$264.16	$264.15	$264.20
Purchase #2	$88.98	12.231%	$99.8631	$99.86	$99.85	$99.90
Purchase #3	$223.90	4.232%	$233.3754	$233.38	$233.40	$233.40
Purchase #4	$7.61	4.442%	$7.948	$7.95	$7.95	$7.90
Purchase #5	$137.50	7.727%	$148.1246	$148.12	$148.10	$148.10
Purchase #6	$202.37	7.511%	$217.57	$217.57	$217.55	$217.60
Purchase #7	$219.73	13.177%	$248.6838	$248.68	$248.70	$248.70
7 purchase totals =	$1,119.54		$1,219.7261	$1,219.72	$1,219.70	$1,219.80