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	$99.71	13.145%	$112.8169	$112.82	$112.80	$112.80
Purchase #2	$159.42	12.259%	$178.9633	$178.96	$178.95	$179.00
Purchase #3	$189.39	4.703%	$198.297	$198.30	$198.30	$198.30
Purchase #4	$192.45	13.167%	$217.7899	$217.79	$217.80	$217.80
Purchase #5	$80.51	11.137%	$89.4764	$89.48	$89.50	$89.50
Purchase #6	$10.31	7.146%	$11.0468	$11.05	$11.05	$11.00
Purchase #7	$127.29	10.199%	$140.2723	$140.27	$140.25	$140.30
7 purchase totals =	$859.08		$948.6626	$948.67	$948.65	$948.70