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	$185.64	7.845%	$200.2035	$200.20	$200.20	$200.20
Purchase #2	$56.91	8.411%	$61.6967	$61.70	$61.70	$61.70
Purchase #3	$211.51	8.513%	$229.5158	$229.52	$229.50	$229.50
Purchase #4	$189.45	11.579%	$211.3864	$211.39	$211.40	$211.40
Purchase #5	$213.50	5.846%	$225.9812	$225.98	$226.00	$226.00
Purchase #6	$187.68	4.708%	$196.516	$196.52	$196.50	$196.50
Purchase #7	$230.83	10.682%	$255.4873	$255.49	$255.50	$255.50
7 purchase totals =	$1,275.52		$1,380.7869	$1,380.80	$1,380.80	$1,380.80