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	$98.43	13.389%	$111.6088	$111.61	$111.60	$111.60
Purchase #2	$82.98	12.227%	$93.126	$93.13	$93.15	$93.10
Purchase #3	$130.25	3.361%	$134.6277	$134.63	$134.65	$134.60
Purchase #4	$16.53	13.331%	$18.7336	$18.73	$18.75	$18.70
Purchase #5	$177.84	3.734%	$184.4805	$184.48	$184.50	$184.50
Purchase #6	$140.75	4.805%	$147.513	$147.51	$147.50	$147.50
Purchase #7	$156.69	6.810%	$167.3606	$167.36	$167.35	$167.40
7 purchase totals =	$803.47		$857.4502	$857.45	$857.50	$857.40