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	$65.80	8.556%	$71.4298	$71.43	$71.45	$71.40
Purchase #2	$150.93	9.824%	$165.7574	$165.76	$165.75	$165.80
Purchase #3	$80.70	13.545%	$91.6308	$91.63	$91.65	$91.60
Purchase #4	$70.64	11.291%	$78.616	$78.62	$78.60	$78.60
Purchase #5	$37.74	4.158%	$39.3092	$39.31	$39.30	$39.30
Purchase #6	$175.58	13.116%	$198.6091	$198.61	$198.60	$198.60
Purchase #7	$105.41	13.246%	$119.3726	$119.37	$119.35	$119.40
7 purchase totals =	$686.80		$764.7249	$764.73	$764.70	$764.70