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	$100.60	9.196%	$109.8512	$109.85	$109.85	$109.90
Purchase #2	$63.68	12.357%	$71.5489	$71.55	$71.55	$71.50
Purchase #3	$42.62	7.259%	$45.7138	$45.71	$45.70	$45.70
Purchase #4	$104.70	6.150%	$111.1391	$111.14	$111.15	$111.10
Purchase #5	$177.41	4.495%	$185.3846	$185.38	$185.40	$185.40
Purchase #6	$172.40	4.776%	$180.6338	$180.63	$180.65	$180.60
Purchase #7	$248.43	8.353%	$269.1814	$269.18	$269.20	$269.20
7 purchase totals =	$909.84		$973.4528	$973.44	$973.50	$973.40