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	$13.94	3.497%	$14.4275	$14.43	$14.45	$14.40
Purchase #2	$16.59	13.534%	$18.8353	$18.84	$18.85	$18.80
Purchase #3	$198.57	12.417%	$223.2264	$223.23	$223.25	$223.20
Purchase #4	$221.51	10.505%	$244.7796	$244.78	$244.80	$244.80
Purchase #5	$91.44	8.803%	$99.4895	$99.49	$99.50	$99.50
Purchase #6	$250.55	9.757%	$274.9962	$275.00	$275.00	$275.00
Purchase #7	$153.65	9.596%	$168.3943	$168.39	$168.40	$168.40
7 purchase totals =	$946.25		$1,044.1488	$1,044.16	$1,044.25	$1,044.10