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	$109.63	5.784%	$115.971	$115.97	$115.95	$116.00
Purchase #2	$73.73	9.250%	$80.55	$80.55	$80.55	$80.60
Purchase #3	$204.49	6.345%	$217.4649	$217.46	$217.45	$217.50
Purchase #4	$87.70	13.134%	$99.2185	$99.22	$99.20	$99.20
Purchase #5	$105.69	6.451%	$112.5081	$112.51	$112.50	$112.50
Purchase #6	$46.81	7.429%	$50.2875	$50.29	$50.30	$50.30
Purchase #7	$78.70	12.181%	$88.2864	$88.29	$88.30	$88.30
7 purchase totals =	$706.75		$764.2864	$764.29	$764.25	$764.40