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	$130.87	13.709%	$148.811	$148.81	$148.80	$148.80
Purchase #2	$33.56	11.334%	$37.3637	$37.36	$37.35	$37.40
Purchase #3	$70.39	3.569%	$72.9022	$72.90	$72.90	$72.90
Purchase #4	$56.63	13.530%	$64.292	$64.29	$64.30	$64.30
Purchase #5	$180.57	7.758%	$194.5786	$194.58	$194.60	$194.60
Purchase #6	$200.27	12.726%	$225.7564	$225.76	$225.75	$225.80
Purchase #7	$154.27	4.351%	$160.9823	$160.98	$161.00	$161.00
7 purchase totals =	$826.56		$904.6862	$904.68	$904.70	$904.80