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	$99.62	5.184%	$104.7843	$104.78	$104.80	$104.80
Purchase #2	$41.72	11.727%	$46.6125	$46.61	$46.60	$46.60
Purchase #3	$171.30	13.238%	$193.9767	$193.98	$194.00	$194.00
Purchase #4	$167.73	4.535%	$175.3366	$175.34	$175.35	$175.30
Purchase #5	$144.82	13.573%	$164.4764	$164.48	$164.50	$164.50
Purchase #6	$111.44	11.698%	$124.4763	$124.48	$124.50	$124.50
Purchase #7	$231.66	9.574%	$253.8391	$253.84	$253.85	$253.80
7 purchase totals =	$968.29		$1,063.5019	$1,063.51	$1,063.60	$1,063.50