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	$102.83	8.406%	$111.4739	$111.47	$111.45	$111.50
Purchase #2	$232.68	13.180%	$263.3472	$263.35	$263.35	$263.30
Purchase #3	$85.79	4.131%	$89.334	$89.33	$89.35	$89.30
Purchase #4	$109.51	6.306%	$116.4157	$116.42	$116.40	$116.40
Purchase #5	$152.40	6.456%	$162.2389	$162.24	$162.25	$162.20
Purchase #6	$26.85	6.213%	$28.5182	$28.52	$28.50	$28.50
Purchase #7	$187.70	8.677%	$203.9867	$203.99	$204.00	$204.00
7 purchase totals =	$897.76		$975.3146	$975.32	$975.30	$975.20