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	$53.29	11.115%	$59.2132	$59.21	$59.20	$59.20
Purchase #2	$31.31	10.302%	$34.5356	$34.54	$34.55	$34.50
Purchase #3	$245.31	11.370%	$273.2017	$273.20	$273.20	$273.20
Purchase #4	$86.59	3.230%	$89.3869	$89.39	$89.40	$89.40
Purchase #5	$121.41	4.674%	$127.0847	$127.08	$127.10	$127.10
Purchase #6	$131.80	11.329%	$146.7316	$146.73	$146.75	$146.70
Purchase #7	$237.75	7.321%	$255.1557	$255.16	$255.15	$255.20
7 purchase totals =	$907.46		$985.3094	$985.31	$985.35	$985.30