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	$130.53	12.313%	$146.6022	$146.60	$146.60	$146.60
Purchase #2	$123.53	9.267%	$134.9775	$134.98	$135.00	$135.00
Purchase #3	$60.80	6.842%	$64.9599	$64.96	$64.95	$65.00
Purchase #4	$73.45	12.146%	$82.3712	$82.37	$82.35	$82.40
Purchase #5	$196.85	9.648%	$215.8421	$215.84	$215.85	$215.80
Purchase #6	$152.42	5.530%	$160.8488	$160.85	$160.85	$160.80
Purchase #7	$62.88	13.553%	$71.4021	$71.40	$71.40	$71.40
7 purchase totals =	$800.46		$877.0038	$877.00	$877.00	$877.00