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	$96.58	3.286%	$99.7536	$99.75	$99.75	$99.80
Purchase #2	$78.64	3.259%	$81.2029	$81.20	$81.20	$81.20
Purchase #3	$87.89	6.278%	$93.4077	$93.41	$93.40	$93.40
Purchase #4	$17.98	4.478%	$18.7851	$18.79	$18.80	$18.80
Purchase #5	$98.92	12.746%	$111.5283	$111.53	$111.55	$111.50
Purchase #6	$104.85	8.602%	$113.8692	$113.87	$113.85	$113.90
Purchase #7	$190.30	11.581%	$212.3386	$212.34	$212.35	$212.30
7 purchase totals =	$675.16		$730.8854	$730.89	$730.90	$730.90