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	$96.79	7.656%	$104.2002	$104.20	$104.20	$104.20
Purchase #2	$112.63	9.425%	$123.2454	$123.25	$123.25	$123.20
Purchase #3	$215.50	6.424%	$229.3437	$229.34	$229.35	$229.30
Purchase #4	$76.93	8.270%	$83.2921	$83.29	$83.30	$83.30
Purchase #5	$241.98	10.218%	$266.7055	$266.71	$266.70	$266.70
Purchase #6	$131.43	10.150%	$144.7701	$144.77	$144.75	$144.80
Purchase #7	$126.35	5.141%	$132.8457	$132.85	$132.85	$132.80
7 purchase totals =	$1,001.61		$1,084.4027	$1,084.41	$1,084.40	$1,084.30