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	$165.70	13.179%	$187.5376	$187.54	$187.55	$187.50
Purchase #2	$167.42	4.126%	$174.3277	$174.33	$174.35	$174.30
Purchase #3	$42.41	12.250%	$47.6052	$47.61	$47.60	$47.60
Purchase #4	$74.44	12.364%	$83.6438	$83.64	$83.65	$83.60
Purchase #5	$53.61	3.586%	$55.5325	$55.53	$55.55	$55.50
Purchase #6	$50.35	5.358%	$53.0478	$53.05	$53.05	$53.00
Purchase #7	$184.95	7.359%	$198.5605	$198.56	$198.55	$198.60
7 purchase totals =	$738.88		$800.2551	$800.26	$800.30	$800.10