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	$61.46	9.405%	$67.2403	$67.24	$67.25	$67.20
Purchase #2	$57.76	6.723%	$61.6432	$61.64	$61.65	$61.60
Purchase #3	$190.70	9.693%	$209.1846	$209.18	$209.20	$209.20
Purchase #4	$75.82	12.626%	$85.393	$85.39	$85.40	$85.40
Purchase #5	$43.48	12.407%	$48.8746	$48.87	$48.85	$48.90
Purchase #6	$198.83	8.245%	$215.2235	$215.22	$215.20	$215.20
Purchase #7	$35.34	4.612%	$36.9699	$36.97	$36.95	$37.00
7 purchase totals =	$663.39		$724.5291	$724.51	$724.50	$724.50