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	$110.71	6.305%	$117.6903	$117.69	$117.70	$117.70
Purchase #2	$83.54	7.671%	$89.9484	$89.95	$89.95	$89.90
Purchase #3	$78.62	8.213%	$85.0771	$85.08	$85.10	$85.10
Purchase #4	$63.57	13.392%	$72.0833	$72.08	$72.10	$72.10
Purchase #5	$132.99	13.593%	$151.0673	$151.07	$151.05	$151.10
Purchase #6	$153.40	8.451%	$166.3638	$166.36	$166.35	$166.40
Purchase #7	$70.50	3.510%	$72.9746	$72.97	$72.95	$73.00
7 purchase totals =	$693.33		$755.2048	$755.20	$755.20	$755.30