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	$247.52	4.582%	$258.8614	$258.86	$258.85	$258.90
Purchase #2	$25.93	9.281%	$28.3366	$28.34	$28.35	$28.30
Purchase #3	$152.58	5.817%	$161.4556	$161.46	$161.45	$161.50
Purchase #4	$243.57	12.593%	$274.2428	$274.24	$274.25	$274.20
Purchase #5	$115.98	7.383%	$124.5428	$124.54	$124.55	$124.50
Purchase #6	$199.51	12.192%	$223.8343	$223.83	$223.85	$223.80
Purchase #7	$29.62	7.613%	$31.875	$31.88	$31.90	$31.90
7 purchase totals =	$1,014.71		$1,103.1485	$1,103.15	$1,103.20	$1,103.10