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	$197.38	4.601%	$206.4615	$206.46	$206.45	$206.50
Purchase #2	$247.46	6.158%	$262.6986	$262.70	$262.70	$262.70
Purchase #3	$248.89	13.192%	$281.7236	$281.72	$281.70	$281.70
Purchase #4	$45.64	9.458%	$49.9566	$49.96	$49.95	$50.00
Purchase #5	$42.46	13.552%	$48.2142	$48.21	$48.20	$48.20
Purchase #6	$68.84	13.507%	$78.1382	$78.14	$78.15	$78.10
Purchase #7	$174.56	6.125%	$185.2518	$185.25	$185.25	$185.30
7 purchase totals =	$1,025.23		$1,112.4445	$1,112.44	$1,112.40	$1,112.50