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	$174.56	9.431%	$191.0228	$191.02	$191.00	$191.00
Purchase #2	$37.57	12.167%	$42.1411	$42.14	$42.15	$42.10
Purchase #3	$226.49	7.400%	$243.2503	$243.25	$243.25	$243.30
Purchase #4	$90.84	10.192%	$100.0984	$100.10	$100.10	$100.10
Purchase #5	$86.49	5.166%	$90.9581	$90.96	$90.95	$91.00
Purchase #6	$29.71	10.457%	$32.8168	$32.82	$32.80	$32.80
Purchase #7	$98.41	10.561%	$108.8031	$108.80	$108.80	$108.80
7 purchase totals =	$744.07		$809.0906	$809.09	$809.05	$809.10