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	$62.48	6.383%	$66.4681	$66.47	$66.45	$66.50
Purchase #2	$213.48	4.774%	$223.6715	$223.67	$223.65	$223.70
Purchase #3	$93.36	3.316%	$96.4558	$96.46	$96.45	$96.50
Purchase #4	$235.98	12.502%	$265.4822	$265.48	$265.50	$265.50
Purchase #5	$134.41	12.574%	$151.3107	$151.31	$151.30	$151.30
Purchase #6	$146.42	7.783%	$157.8159	$157.82	$157.80	$157.80
Purchase #7	$134.62	6.609%	$143.517	$143.52	$143.50	$143.50
7 purchase totals =	$1,020.75		$1,104.7212	$1,104.73	$1,104.65	$1,104.80