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	$250.31	7.781%	$269.7866	$269.79	$269.80	$269.80
Purchase #2	$248.89	7.849%	$268.4254	$268.43	$268.45	$268.40
Purchase #3	$109.42	3.701%	$113.4696	$113.47	$113.45	$113.50
Purchase #4	$28.86	10.874%	$31.9982	$32.00	$32.00	$32.00
Purchase #5	$23.74	7.532%	$25.5281	$25.53	$25.55	$25.50
Purchase #6	$121.35	7.857%	$130.8845	$130.88	$130.90	$130.90
Purchase #7	$172.95	10.727%	$191.5023	$191.50	$191.50	$191.50
7 purchase totals =	$955.52		$1,031.5947	$1,031.60	$1,031.65	$1,031.60