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	$96.59	9.167%	$105.4444	$105.44	$105.45	$105.40
Purchase #2	$75.28	9.700%	$82.5822	$82.58	$82.60	$82.60
Purchase #3	$26.80	6.828%	$28.6299	$28.63	$28.65	$28.60
Purchase #4	$10.32	5.484%	$10.8859	$10.89	$10.90	$10.90
Purchase #5	$213.28	9.359%	$233.2409	$233.24	$233.25	$233.20
Purchase #6	$45.43	10.402%	$50.1556	$50.16	$50.15	$50.20
Purchase #7	$83.29	4.159%	$86.754	$86.75	$86.75	$86.80
7 purchase totals =	$550.99		$597.6929	$597.69	$597.75	$597.70