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	$78.97	9.585%	$86.5393	$86.54	$86.55	$86.50
Purchase #2	$57.85	6.568%	$61.6496	$61.65	$61.65	$61.60
Purchase #3	$61.56	4.657%	$64.4268	$64.43	$64.45	$64.40
Purchase #4	$23.66	8.264%	$25.6153	$25.62	$25.60	$25.60
Purchase #5	$87.47	10.413%	$96.5783	$96.58	$96.60	$96.60
Purchase #6	$58.29	12.484%	$65.5669	$65.57	$65.55	$65.60
Purchase #7	$74.95	4.674%	$78.4532	$78.45	$78.45	$78.50
7 purchase totals =	$442.75		$478.8294	$478.84	$478.85	$478.80