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	$216.78	6.865%	$231.6619	$231.66	$231.65	$231.70
Purchase #2	$197.51	5.312%	$208.0017	$208.00	$208.00	$208.00
Purchase #3	$207.93	9.761%	$228.226	$228.23	$228.25	$228.20
Purchase #4	$150.45	11.571%	$167.8586	$167.86	$167.85	$167.90
Purchase #5	$160.34	13.277%	$181.6283	$181.63	$181.65	$181.60
Purchase #6	$79.27	12.650%	$89.2977	$89.30	$89.30	$89.30
Purchase #7	$191.29	13.238%	$216.613	$216.61	$216.60	$216.60
7 purchase totals =	$1,203.57		$1,323.2872	$1,323.29	$1,323.30	$1,323.30