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	$62.49	6.561%	$66.59	$66.59	$66.60	$66.60
Purchase #2	$91.62	8.446%	$99.3582	$99.36	$99.35	$99.40
Purchase #3	$238.82	8.503%	$259.1269	$259.13	$259.15	$259.10
Purchase #4	$129.87	10.526%	$143.5401	$143.54	$143.55	$143.50
Purchase #5	$83.93	13.851%	$95.5551	$95.56	$95.55	$95.60
Purchase #6	$191.43	6.643%	$204.1467	$204.15	$204.15	$204.10
Purchase #7	$98.60	6.181%	$104.6945	$104.69	$104.70	$104.70
7 purchase totals =	$896.76		$973.0115	$973.02	$973.05	$973.00