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	$67.77	7.398%	$72.7836	$72.78	$72.80	$72.80
Purchase #2	$104.67	5.489%	$110.4153	$110.42	$110.40	$110.40
Purchase #3	$152.82	12.716%	$172.2526	$172.25	$172.25	$172.30
Purchase #4	$218.75	13.581%	$248.4584	$248.46	$248.45	$248.50
Purchase #5	$176.73	7.745%	$190.4177	$190.42	$190.40	$190.40
Purchase #6	$160.64	12.177%	$180.2011	$180.20	$180.20	$180.20
Purchase #7	$33.29	7.441%	$35.7671	$35.77	$35.75	$35.80
7 purchase totals =	$914.67		$1,010.2958	$1,010.30	$1,010.25	$1,010.40