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	$190.43	5.513%	$200.9284	$200.93	$200.95	$200.90
Purchase #2	$78.45	10.706%	$86.8489	$86.85	$86.85	$86.80
Purchase #3	$99.97	3.665%	$103.6339	$103.63	$103.65	$103.60
Purchase #4	$153.97	6.652%	$164.2121	$164.21	$164.20	$164.20
Purchase #5	$89.68	13.237%	$101.5509	$101.55	$101.55	$101.60
Purchase #6	$160.52	7.608%	$172.7324	$172.73	$172.75	$172.70
Purchase #7	$75.63	10.329%	$83.4418	$83.44	$83.45	$83.40
7 purchase totals =	$848.65		$913.3484	$913.34	$913.40	$913.20