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	$93.63	8.159%	$101.2693	$101.27	$101.25	$101.30
Purchase #2	$230.54	6.199%	$244.8312	$244.83	$244.85	$244.80
Purchase #3	$152.28	10.121%	$167.6923	$167.69	$167.70	$167.70
Purchase #4	$36.38	12.168%	$40.8067	$40.81	$40.80	$40.80
Purchase #5	$218.70	9.112%	$238.6279	$238.63	$238.65	$238.60
Purchase #6	$215.60	8.147%	$233.1649	$233.16	$233.15	$233.20
Purchase #7	$55.30	9.366%	$60.4794	$60.48	$60.50	$60.50
7 purchase totals =	$1,002.43		$1,086.8717	$1,086.87	$1,086.90	$1,086.90