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	$246.56	7.401%	$264.8079	$264.81	$264.80	$264.80
Purchase #2	$64.89	3.245%	$66.9957	$67.00	$67.00	$67.00
Purchase #3	$96.83	13.104%	$109.5186	$109.52	$109.50	$109.50
Purchase #4	$150.59	9.696%	$165.1912	$165.19	$165.20	$165.20
Purchase #5	$179.53	5.273%	$188.9966	$189.00	$189.00	$189.00
Purchase #6	$6.42	6.458%	$6.8346	$6.83	$6.85	$6.80
Purchase #7	$165.39	4.510%	$172.8491	$172.85	$172.85	$172.80
7 purchase totals =	$910.21		$975.1937	$975.20	$975.20	$975.10