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	$126.53	12.419%	$142.2438	$142.24	$142.25	$142.20
Purchase #2	$48.72	7.694%	$52.4685	$52.47	$52.45	$52.50
Purchase #3	$47.74	3.725%	$49.5183	$49.52	$49.50	$49.50
Purchase #4	$94.31	5.456%	$99.4556	$99.46	$99.45	$99.50
Purchase #5	$67.57	5.486%	$71.2769	$71.28	$71.30	$71.30
Purchase #6	$216.27	5.207%	$227.5312	$227.53	$227.55	$227.50
Purchase #7	$234.48	11.663%	$261.8274	$261.83	$261.85	$261.80
7 purchase totals =	$835.62		$904.3217	$904.33	$904.35	$904.30