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	$110.81	5.451%	$116.8503	$116.85	$116.85	$116.90
Purchase #2	$37.26	9.873%	$40.9387	$40.94	$40.95	$40.90
Purchase #3	$63.84	3.670%	$66.1829	$66.18	$66.20	$66.20
Purchase #4	$140.74	6.746%	$150.2343	$150.23	$150.25	$150.20
Purchase #5	$204.83	4.186%	$213.4042	$213.40	$213.40	$213.40
Purchase #6	$109.96	5.607%	$116.1255	$116.13	$116.15	$116.10
Purchase #7	$210.96	5.558%	$222.6852	$222.69	$222.70	$222.70
7 purchase totals =	$878.40		$926.4211	$926.42	$926.50	$926.40