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	$28.83	10.673%	$31.907	$31.91	$31.90	$31.90
Purchase #2	$47.70	11.218%	$53.051	$53.05	$53.05	$53.10
Purchase #3	$13.70	8.473%	$14.8608	$14.86	$14.85	$14.90
Purchase #4	$49.46	11.710%	$55.2518	$55.25	$55.25	$55.30
Purchase #5	$117.82	5.290%	$124.0527	$124.05	$124.05	$124.10
Purchase #6	$125.92	12.375%	$141.5026	$141.50	$141.50	$141.50
Purchase #7	$6.96	11.391%	$7.7528	$7.75	$7.75	$7.80
7 purchase totals =	$390.39		$428.3787	$428.37	$428.35	$428.60