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	$106.54	11.524%	$118.8177	$118.82	$118.80	$118.80
Purchase #2	$243.72	8.438%	$264.2851	$264.29	$264.30	$264.30
Purchase #3	$217.86	9.590%	$238.7528	$238.75	$238.75	$238.80
Purchase #4	$206.48	7.527%	$222.0217	$222.02	$222.00	$222.00
Purchase #5	$12.98	3.548%	$13.4405	$13.44	$13.45	$13.40
Purchase #6	$121.57	12.753%	$137.0738	$137.07	$137.05	$137.10
Purchase #7	$92.58	7.540%	$99.5605	$99.56	$99.55	$99.60
7 purchase totals =	$1,001.73		$1,093.9521	$1,093.95	$1,093.90	$1,094.00