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	$77.93	7.270%	$83.5955	$83.60	$83.60	$83.60
Purchase #2	$105.94	12.658%	$119.3499	$119.35	$119.35	$119.30
Purchase #3	$74.50	8.563%	$80.8794	$80.88	$80.90	$80.90
Purchase #4	$127.54	10.224%	$140.5797	$140.58	$140.60	$140.60
Purchase #5	$102.89	11.701%	$114.9292	$114.93	$114.95	$114.90
Purchase #6	$32.91	10.584%	$36.3932	$36.39	$36.40	$36.40
Purchase #7	$120.73	5.572%	$127.4571	$127.46	$127.45	$127.50
7 purchase totals =	$642.44		$703.1840	$703.19	$703.25	$703.20