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	$169.84	7.656%	$182.843	$182.84	$182.85	$182.80
Purchase #2	$100.74	11.204%	$112.0269	$112.03	$112.05	$112.00
Purchase #3	$127.74	6.608%	$136.1811	$136.18	$136.20	$136.20
Purchase #4	$197.39	4.274%	$205.8264	$205.83	$205.85	$205.80
Purchase #5	$96.54	6.853%	$103.1559	$103.16	$103.15	$103.20
Purchase #6	$178.47	7.210%	$191.3377	$191.34	$191.35	$191.30
Purchase #7	$141.34	8.575%	$153.4599	$153.46	$153.45	$153.50
7 purchase totals =	$1,012.06		$1,084.8309	$1,084.84	$1,084.90	$1,084.80