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	$209.80	7.352%	$225.2245	$225.22	$225.20	$225.20
Purchase #2	$222.31	5.232%	$233.9413	$233.94	$233.95	$233.90
Purchase #3	$85.81	12.873%	$96.8563	$96.86	$96.85	$96.90
Purchase #4	$160.88	9.230%	$175.7292	$175.73	$175.75	$175.70
Purchase #5	$149.26	5.492%	$157.4574	$157.46	$157.45	$157.50
Purchase #6	$88.86	13.137%	$100.5335	$100.53	$100.55	$100.50
Purchase #7	$96.68	5.167%	$101.6755	$101.68	$101.70	$101.70
7 purchase totals =	$1,013.60		$1,091.4177	$1,091.42	$1,091.45	$1,091.40