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	$137.65	10.579%	$152.212	$152.21	$152.20	$152.20
Purchase #2	$72.94	4.619%	$76.3091	$76.31	$76.30	$76.30
Purchase #3	$78.70	9.556%	$86.2206	$86.22	$86.20	$86.20
Purchase #4	$39.61	6.553%	$42.2056	$42.21	$42.20	$42.20
Purchase #5	$191.37	4.134%	$199.2812	$199.28	$199.30	$199.30
Purchase #6	$137.60	10.257%	$151.7136	$151.71	$151.70	$151.70
Purchase #7	$147.29	11.855%	$164.7512	$164.75	$164.75	$164.80
7 purchase totals =	$805.16		$872.6933	$872.69	$872.65	$872.70