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	$90.67	4.373%	$94.635	$94.64	$94.65	$94.60
Purchase #2	$92.28	10.528%	$101.9952	$102.00	$102.00	$102.00
Purchase #3	$129.40	12.481%	$145.5504	$145.55	$145.55	$145.60
Purchase #4	$62.96	13.817%	$71.6592	$71.66	$71.65	$71.70
Purchase #5	$34.89	10.603%	$38.5894	$38.59	$38.60	$38.60
Purchase #6	$152.67	12.525%	$171.7919	$171.79	$171.80	$171.80
Purchase #7	$156.68	7.671%	$168.6989	$168.70	$168.70	$168.70
7 purchase totals =	$719.55		$792.9200	$792.93	$792.95	$793.00