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	$119.56	6.495%	$127.3254	$127.33	$127.35	$127.30
Purchase #2	$231.79	4.178%	$241.4742	$241.47	$241.45	$241.50
Purchase #3	$161.72	10.779%	$179.1518	$179.15	$179.15	$179.20
Purchase #4	$232.59	12.466%	$261.5847	$261.58	$261.60	$261.60
Purchase #5	$131.27	4.566%	$137.2638	$137.26	$137.25	$137.30
Purchase #6	$134.90	4.843%	$141.4332	$141.43	$141.45	$141.40
Purchase #7	$18.48	12.252%	$20.7442	$20.74	$20.75	$20.70
7 purchase totals =	$1,030.31		$1,108.9773	$1,108.96	$1,109.00	$1,109.00