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	$41.73	4.165%	$43.4681	$43.47	$43.45	$43.50
Purchase #2	$175.51	11.865%	$196.3343	$196.33	$196.35	$196.30
Purchase #3	$161.40	4.115%	$168.0416	$168.04	$168.05	$168.00
Purchase #4	$26.78	8.528%	$29.0638	$29.06	$29.05	$29.10
Purchase #5	$185.57	12.269%	$208.3376	$208.34	$208.35	$208.30
Purchase #6	$237.84	7.659%	$256.0562	$256.06	$256.05	$256.10
Purchase #7	$137.44	3.726%	$142.561	$142.56	$142.55	$142.60
7 purchase totals =	$966.27		$1,043.8626	$1,043.86	$1,043.85	$1,043.90