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	$151.26	4.192%	$157.6008	$157.60	$157.60	$157.60
Purchase #2	$83.57	8.609%	$90.7645	$90.76	$90.75	$90.80
Purchase #3	$34.89	6.141%	$37.0326	$37.03	$37.05	$37.00
Purchase #4	$128.32	7.375%	$137.7836	$137.78	$137.80	$137.80
Purchase #5	$121.73	4.590%	$127.3174	$127.32	$127.30	$127.30
Purchase #6	$78.43	4.445%	$81.9162	$81.92	$81.90	$81.90
Purchase #7	$56.37	10.404%	$62.2347	$62.23	$62.25	$62.20
7 purchase totals =	$654.57		$694.6498	$694.64	$694.65	$694.60