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	$227.63	12.261%	$255.5397	$255.54	$255.55	$255.50
Purchase #2	$223.30	8.117%	$241.4253	$241.43	$241.45	$241.40
Purchase #3	$195.91	11.426%	$218.2947	$218.29	$218.30	$218.30
Purchase #4	$91.84	10.862%	$101.8157	$101.82	$101.80	$101.80
Purchase #5	$66.40	8.793%	$72.2386	$72.24	$72.25	$72.20
Purchase #6	$210.27	5.583%	$222.0094	$222.01	$222.00	$222.00
Purchase #7	$77.37	10.669%	$85.6246	$85.62	$85.60	$85.60
7 purchase totals =	$1,092.72		$1,196.9480	$1,196.95	$1,196.95	$1,196.80