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	$33.57	11.565%	$37.4524	$37.45	$37.45	$37.50
Purchase #2	$130.31	8.650%	$141.5818	$141.58	$141.60	$141.60
Purchase #3	$246.94	3.218%	$254.8865	$254.89	$254.90	$254.90
Purchase #4	$147.53	13.165%	$166.9523	$166.95	$166.95	$167.00
Purchase #5	$67.44	6.601%	$71.8917	$71.89	$71.90	$71.90
Purchase #6	$12.88	9.583%	$14.1143	$14.11	$14.10	$14.10
Purchase #7	$40.30	13.862%	$45.8864	$45.89	$45.90	$45.90
7 purchase totals =	$678.97		$732.7654	$732.76	$732.80	$732.90