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	$56.65	10.154%	$62.4022	$62.40	$62.40	$62.40
Purchase #2	$175.51	3.524%	$181.695	$181.70	$181.70	$181.70
Purchase #3	$11.73	12.667%	$13.2158	$13.22	$13.20	$13.20
Purchase #4	$34.60	3.661%	$35.8667	$35.87	$35.85	$35.90
Purchase #5	$191.58	12.550%	$215.6233	$215.62	$215.60	$215.60
Purchase #6	$83.59	11.118%	$92.8835	$92.88	$92.90	$92.90
Purchase #7	$54.64	13.424%	$61.9749	$61.97	$61.95	$62.00
7 purchase totals =	$608.30		$663.6614	$663.66	$663.60	$663.70