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	$30.75	5.196%	$32.3478	$32.35	$32.35	$32.30
Purchase #2	$88.64	5.384%	$93.4124	$93.41	$93.40	$93.40
Purchase #3	$162.80	13.614%	$184.9636	$184.96	$184.95	$185.00
Purchase #4	$104.73	10.214%	$115.4271	$115.43	$115.45	$115.40
Purchase #5	$98.81	12.684%	$111.3431	$111.34	$111.35	$111.30
Purchase #6	$48.53	4.254%	$50.5945	$50.59	$50.60	$50.60
Purchase #7	$164.75	9.556%	$180.4935	$180.49	$180.50	$180.50
7 purchase totals =	$699.01		$768.5820	$768.57	$768.60	$768.50