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	$149.62	6.832%	$159.842	$159.84	$159.85	$159.80
Purchase #2	$142.88	6.191%	$151.7257	$151.73	$151.75	$151.70
Purchase #3	$16.55	9.799%	$18.1717	$18.17	$18.15	$18.20
Purchase #4	$248.95	6.275%	$264.5716	$264.57	$264.55	$264.60
Purchase #5	$75.80	12.481%	$85.2606	$85.26	$85.25	$85.30
Purchase #6	$176.31	13.728%	$200.5138	$200.51	$200.50	$200.50
Purchase #7	$21.85	12.316%	$24.541	$24.54	$24.55	$24.50
7 purchase totals =	$831.96		$904.6264	$904.62	$904.60	$904.60