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	$177.29	13.297%	$200.8643	$200.86	$200.85	$200.90
Purchase #2	$49.27	13.472%	$55.9077	$55.91	$55.90	$55.90
Purchase #3	$245.54	7.443%	$263.8155	$263.82	$263.80	$263.80
Purchase #4	$7.83	12.653%	$8.8207	$8.82	$8.80	$8.80
Purchase #5	$54.38	3.184%	$56.1115	$56.11	$56.10	$56.10
Purchase #6	$247.44	6.524%	$263.583	$263.58	$263.60	$263.60
Purchase #7	$86.68	5.252%	$91.2324	$91.23	$91.25	$91.20
7 purchase totals =	$868.43		$940.3351	$940.33	$940.30	$940.30