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	$193.38	7.769%	$208.4037	$208.40	$208.40	$208.40
Purchase #2	$151.34	11.597%	$168.8909	$168.89	$168.90	$168.90
Purchase #3	$193.64	10.188%	$213.368	$213.37	$213.35	$213.40
Purchase #4	$9.47	9.442%	$10.3642	$10.36	$10.35	$10.40
Purchase #5	$81.93	8.856%	$89.1857	$89.19	$89.20	$89.20
Purchase #6	$98.96	5.460%	$104.3632	$104.36	$104.35	$104.40
Purchase #7	$79.90	12.611%	$89.9762	$89.98	$90.00	$90.00
7 purchase totals =	$808.62		$884.5519	$884.55	$884.55	$884.70