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	$67.37	4.110%	$70.1389	$70.14	$70.15	$70.10
Purchase #2	$229.67	10.786%	$254.4422	$254.44	$254.45	$254.40
Purchase #3	$164.29	11.107%	$182.5377	$182.54	$182.55	$182.50
Purchase #4	$26.43	13.306%	$29.9468	$29.95	$29.95	$29.90
Purchase #5	$43.78	4.408%	$45.7098	$45.71	$45.70	$45.70
Purchase #6	$75.87	3.306%	$78.3783	$78.38	$78.40	$78.40
Purchase #7	$246.69	13.726%	$280.5507	$280.55	$280.55	$280.60
7 purchase totals =	$854.10		$941.7044	$941.71	$941.75	$941.60