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	$180.90	8.689%	$196.6184	$196.62	$196.60	$196.60
Purchase #2	$235.94	3.820%	$244.9529	$244.95	$244.95	$245.00
Purchase #3	$237.29	8.235%	$256.8308	$256.83	$256.85	$256.80
Purchase #4	$29.43	6.371%	$31.305	$31.31	$31.30	$31.30
Purchase #5	$101.88	7.214%	$109.2296	$109.23	$109.25	$109.20
Purchase #6	$137.44	6.698%	$146.6457	$146.65	$146.65	$146.60
Purchase #7	$46.89	4.210%	$48.8641	$48.86	$48.85	$48.90
7 purchase totals =	$969.77		$1,034.4465	$1,034.45	$1,034.45	$1,034.40