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	$215.78	13.679%	$245.2965	$245.30	$245.30	$245.30
Purchase #2	$243.53	10.295%	$268.6014	$268.60	$268.60	$268.60
Purchase #3	$7.64	9.561%	$8.3705	$8.37	$8.35	$8.40
Purchase #4	$95.77	7.136%	$102.6041	$102.60	$102.60	$102.60
Purchase #5	$103.83	7.818%	$111.9474	$111.95	$111.95	$111.90
Purchase #6	$33.72	3.340%	$34.8462	$34.85	$34.85	$34.80
Purchase #7	$61.71	6.677%	$65.8304	$65.83	$65.85	$65.80
7 purchase totals =	$761.98		$837.4965	$837.50	$837.50	$837.40