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	$195.31	10.711%	$216.2297	$216.23	$216.25	$216.20
Purchase #2	$83.56	10.733%	$92.5285	$92.53	$92.55	$92.50
Purchase #3	$38.97	8.367%	$42.2306	$42.23	$42.25	$42.20
Purchase #4	$156.35	9.547%	$171.2767	$171.28	$171.30	$171.30
Purchase #5	$25.93	12.444%	$29.1567	$29.16	$29.15	$29.20
Purchase #6	$58.81	8.435%	$63.7706	$63.77	$63.75	$63.80
Purchase #7	$165.76	9.403%	$181.3464	$181.35	$181.35	$181.30
7 purchase totals =	$724.69		$796.5392	$796.55	$796.60	$796.50