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	$43.67	5.112%	$45.9024	$45.90	$45.90	$45.90
Purchase #2	$97.54	3.684%	$101.1334	$101.13	$101.15	$101.10
Purchase #3	$37.59	10.245%	$41.4411	$41.44	$41.45	$41.40
Purchase #4	$90.99	5.746%	$96.2183	$96.22	$96.20	$96.20
Purchase #5	$39.72	8.792%	$43.2122	$43.21	$43.20	$43.20
Purchase #6	$93.63	8.721%	$101.7955	$101.80	$101.80	$101.80
Purchase #7	$229.59	3.659%	$237.9907	$237.99	$238.00	$238.00
7 purchase totals =	$632.73		$667.6936	$667.69	$667.70	$667.60