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	$44.64	5.333%	$47.0207	$47.02	$47.00	$47.00
Purchase #2	$57.50	6.451%	$61.2093	$61.21	$61.20	$61.20
Purchase #3	$168.62	10.796%	$186.8242	$186.82	$186.80	$186.80
Purchase #4	$83.57	11.156%	$92.8931	$92.89	$92.90	$92.90
Purchase #5	$72.50	10.327%	$79.9871	$79.99	$80.00	$80.00
Purchase #6	$29.78	13.120%	$33.6871	$33.69	$33.70	$33.70
Purchase #7	$28.40	8.764%	$30.889	$30.89	$30.90	$30.90
7 purchase totals =	$485.01		$532.5105	$532.51	$532.50	$532.50