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	$150.64	4.570%	$157.5242	$157.52	$157.50	$157.50
Purchase #2	$64.86	10.478%	$71.656	$71.66	$71.65	$71.70
Purchase #3	$85.42	9.743%	$93.7425	$93.74	$93.75	$93.70
Purchase #4	$44.33	9.415%	$48.5037	$48.50	$48.50	$48.50
Purchase #5	$6.87	10.461%	$7.5887	$7.59	$7.60	$7.60
Purchase #6	$96.34	4.511%	$100.6859	$100.69	$100.70	$100.70
Purchase #7	$12.59	9.224%	$13.7513	$13.75	$13.75	$13.80
7 purchase totals =	$461.05		$493.4523	$493.45	$493.45	$493.50