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	$236.94	9.271%	$258.9067	$258.91	$258.90	$258.90
Purchase #2	$96.75	13.539%	$109.849	$109.85	$109.85	$109.80
Purchase #3	$175.75	11.773%	$196.441	$196.44	$196.45	$196.40
Purchase #4	$175.65	7.626%	$189.0451	$189.05	$189.05	$189.00
Purchase #5	$133.26	13.764%	$151.6019	$151.60	$151.60	$151.60
Purchase #6	$156.65	10.595%	$173.2471	$173.25	$173.25	$173.20
Purchase #7	$60.46	5.214%	$63.6124	$63.61	$63.60	$63.60
7 purchase totals =	$1,035.46		$1,142.7032	$1,142.71	$1,142.70	$1,142.50