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	$235.79	3.202%	$243.34	$243.34	$243.35	$243.30
Purchase #2	$87.58	3.515%	$90.6584	$90.66	$90.65	$90.70
Purchase #3	$130.36	10.575%	$144.1456	$144.15	$144.15	$144.10
Purchase #4	$184.26	8.231%	$199.4264	$199.43	$199.45	$199.40
Purchase #5	$40.46	7.190%	$43.3691	$43.37	$43.35	$43.40
Purchase #6	$213.65	12.438%	$240.2238	$240.22	$240.20	$240.20
Purchase #7	$38.85	5.144%	$40.8484	$40.85	$40.85	$40.80
7 purchase totals =	$930.95		$1,002.0117	$1,002.02	$1,002.00	$1,001.90