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	$53.84	9.799%	$59.1158	$59.12	$59.10	$59.10
Purchase #2	$37.27	12.169%	$41.8054	$41.81	$41.80	$41.80
Purchase #3	$33.67	12.215%	$37.7828	$37.78	$37.80	$37.80
Purchase #4	$188.96	7.699%	$203.508	$203.51	$203.50	$203.50
Purchase #5	$129.73	6.213%	$137.7901	$137.79	$137.80	$137.80
Purchase #6	$99.78	3.281%	$103.0538	$103.05	$103.05	$103.10
Purchase #7	$244.56	7.379%	$262.6061	$262.61	$262.60	$262.60
7 purchase totals =	$787.81		$845.6620	$845.67	$845.65	$845.70