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	$11.54	4.346%	$12.0415	$12.04	$12.05	$12.00
Purchase #2	$97.71	6.400%	$103.9634	$103.96	$103.95	$104.00
Purchase #3	$230.90	11.189%	$256.7354	$256.74	$256.75	$256.70
Purchase #4	$171.89	7.565%	$184.8935	$184.89	$184.90	$184.90
Purchase #5	$146.88	8.520%	$159.3942	$159.39	$159.40	$159.40
Purchase #6	$179.46	5.319%	$189.0055	$189.01	$189.00	$189.00
Purchase #7	$103.53	7.705%	$111.507	$111.51	$111.50	$111.50
7 purchase totals =	$941.91		$1,017.5405	$1,017.54	$1,017.55	$1,017.50