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	$196.27	7.725%	$211.4319	$211.43	$211.45	$211.40
Purchase #2	$118.89	3.845%	$123.4613	$123.46	$123.45	$123.50
Purchase #3	$57.88	9.242%	$63.2293	$63.23	$63.25	$63.20
Purchase #4	$8.45	12.740%	$9.5265	$9.53	$9.55	$9.50
Purchase #5	$29.34	11.860%	$32.8197	$32.82	$32.80	$32.80
Purchase #6	$51.40	8.294%	$55.6631	$55.66	$55.65	$55.70
Purchase #7	$12.71	9.495%	$13.9168	$13.92	$13.90	$13.90
7 purchase totals =	$474.94		$510.0486	$510.05	$510.05	$510.00