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	$197.53	12.597%	$222.4129	$222.41	$222.40	$222.40
Purchase #2	$50.87	7.271%	$54.5688	$54.57	$54.55	$54.60
Purchase #3	$240.61	10.691%	$266.3336	$266.33	$266.35	$266.30
Purchase #4	$149.49	11.336%	$166.4362	$166.44	$166.45	$166.40
Purchase #5	$137.39	9.546%	$150.5052	$150.51	$150.50	$150.50
Purchase #6	$159.78	7.295%	$171.436	$171.44	$171.45	$171.40
Purchase #7	$59.75	4.827%	$62.6341	$62.63	$62.65	$62.60
7 purchase totals =	$995.42		$1,094.3268	$1,094.33	$1,094.35	$1,094.20