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	$40.30	10.591%	$44.5682	$44.57	$44.55	$44.60
Purchase #2	$64.82	9.610%	$71.0492	$71.05	$71.05	$71.00
Purchase #3	$105.55	10.745%	$116.8913	$116.89	$116.90	$116.90
Purchase #4	$89.55	8.117%	$96.8188	$96.82	$96.80	$96.80
Purchase #5	$41.81	7.391%	$44.9002	$44.90	$44.90	$44.90
Purchase #6	$246.28	10.104%	$271.1641	$271.16	$271.15	$271.20
Purchase #7	$89.83	4.671%	$94.026	$94.03	$94.05	$94.00
7 purchase totals =	$678.14		$739.4178	$739.42	$739.40	$739.40