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	$175.44	5.787%	$185.5927	$185.59	$185.60	$185.60
Purchase #2	$141.42	11.733%	$158.0128	$158.01	$158.00	$158.00
Purchase #3	$39.84	5.520%	$42.0392	$42.04	$42.05	$42.00
Purchase #4	$70.48	7.868%	$76.0254	$76.03	$76.05	$76.00
Purchase #5	$10.51	4.866%	$11.0214	$11.02	$11.00	$11.00
Purchase #6	$53.98	13.342%	$61.182	$61.18	$61.20	$61.20
Purchase #7	$225.64	4.819%	$236.5136	$236.51	$236.50	$236.50
7 purchase totals =	$717.31		$770.3871	$770.38	$770.40	$770.30