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	$142.51	7.116%	$152.651	$152.65	$152.65	$152.70
Purchase #2	$199.38	5.242%	$209.8315	$209.83	$209.85	$209.80
Purchase #3	$136.75	12.264%	$153.521	$153.52	$153.50	$153.50
Purchase #4	$125.68	13.702%	$142.9007	$142.90	$142.90	$142.90
Purchase #5	$232.52	11.319%	$258.8389	$258.84	$258.85	$258.80
Purchase #6	$19.43	10.375%	$21.4459	$21.45	$21.45	$21.40
Purchase #7	$184.44	13.547%	$209.4261	$209.43	$209.45	$209.40
7 purchase totals =	$1,040.71		$1,148.6151	$1,148.62	$1,148.65	$1,148.50