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	$219.59	7.474%	$236.0022	$236.00	$236.00	$236.00
Purchase #2	$146.97	6.481%	$156.4951	$156.50	$156.50	$156.50
Purchase #3	$213.59	9.251%	$233.3492	$233.35	$233.35	$233.30
Purchase #4	$18.98	6.823%	$20.275	$20.28	$20.30	$20.30
Purchase #5	$86.43	3.785%	$89.7014	$89.70	$89.70	$89.70
Purchase #6	$42.85	7.694%	$46.1469	$46.15	$46.15	$46.10
Purchase #7	$247.49	11.144%	$275.0703	$275.07	$275.05	$275.10
7 purchase totals =	$975.90		$1,057.0401	$1,057.05	$1,057.05	$1,057.00