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	$55.35	10.650%	$61.2448	$61.24	$61.25	$61.20
Purchase #2	$77.61	9.646%	$85.0963	$85.10	$85.10	$85.10
Purchase #3	$127.31	6.467%	$135.5431	$135.54	$135.55	$135.50
Purchase #4	$127.28	12.114%	$142.6987	$142.70	$142.70	$142.70
Purchase #5	$156.80	12.179%	$175.8967	$175.90	$175.90	$175.90
Purchase #6	$38.60	6.213%	$40.9982	$41.00	$41.00	$41.00
Purchase #7	$157.53	9.408%	$172.3504	$172.35	$172.35	$172.40
7 purchase totals =	$740.48		$813.8282	$813.83	$813.85	$813.80