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	$182.68	9.363%	$199.7843	$199.78	$199.80	$199.80
Purchase #2	$25.96	4.187%	$27.0469	$27.05	$27.05	$27.00
Purchase #3	$86.39	12.703%	$97.3641	$97.36	$97.35	$97.40
Purchase #4	$164.81	12.755%	$185.8315	$185.83	$185.85	$185.80
Purchase #5	$18.49	12.375%	$20.7781	$20.78	$20.80	$20.80
Purchase #6	$219.75	13.853%	$250.192	$250.19	$250.20	$250.20
Purchase #7	$203.38	9.140%	$221.9689	$221.97	$221.95	$222.00
7 purchase totals =	$901.46		$1,002.9658	$1,002.96	$1,003.00	$1,003.00