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	$118.88	10.560%	$131.4337	$131.43	$131.45	$131.40
Purchase #2	$193.46	12.122%	$216.9112	$216.91	$216.90	$216.90
Purchase #3	$135.82	4.469%	$141.8898	$141.89	$141.90	$141.90
Purchase #4	$9.38	13.154%	$10.6138	$10.61	$10.60	$10.60
Purchase #5	$15.68	11.626%	$17.503	$17.50	$17.50	$17.50
Purchase #6	$202.88	4.837%	$212.6933	$212.69	$212.70	$212.70
Purchase #7	$30.51	8.378%	$33.0661	$33.07	$33.05	$33.10
7 purchase totals =	$706.61		$764.1109	$764.10	$764.10	$764.10