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	$89.42	5.764%	$94.5742	$94.57	$94.55	$94.60
Purchase #2	$10.36	4.862%	$10.8637	$10.86	$10.85	$10.90
Purchase #3	$189.85	13.695%	$215.85	$215.85	$215.85	$215.90
Purchase #4	$112.66	3.323%	$116.4037	$116.40	$116.40	$116.40
Purchase #5	$116.43	6.529%	$124.0317	$124.03	$124.05	$124.00
Purchase #6	$59.99	5.323%	$63.1833	$63.18	$63.20	$63.20
Purchase #7	$57.44	3.836%	$59.6434	$59.64	$59.65	$59.60
7 purchase totals =	$636.15		$684.5500	$684.53	$684.55	$684.60