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	$175.74	12.321%	$197.3929	$197.39	$197.40	$197.40
Purchase #2	$74.61	11.738%	$83.3677	$83.37	$83.35	$83.40
Purchase #3	$227.27	12.602%	$255.9106	$255.91	$255.90	$255.90
Purchase #4	$190.98	12.601%	$215.0454	$215.05	$215.05	$215.00
Purchase #5	$230.37	6.474%	$245.2842	$245.28	$245.30	$245.30
Purchase #6	$71.59	11.764%	$80.0118	$80.01	$80.00	$80.00
Purchase #7	$152.95	10.146%	$168.4683	$168.47	$168.45	$168.50
7 purchase totals =	$1,123.51		$1,245.4809	$1,245.48	$1,245.45	$1,245.50