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	$22.60	11.104%	$25.1095	$25.11	$25.10	$25.10
Purchase #2	$69.45	13.592%	$78.8896	$78.89	$78.90	$78.90
Purchase #3	$90.47	12.719%	$101.9769	$101.98	$102.00	$102.00
Purchase #4	$237.57	12.619%	$267.549	$267.55	$267.55	$267.50
Purchase #5	$173.54	12.255%	$194.8073	$194.81	$194.80	$194.80
Purchase #6	$89.72	10.619%	$99.2474	$99.25	$99.25	$99.20
Purchase #7	$101.47	12.201%	$113.8504	$113.85	$113.85	$113.90
7 purchase totals =	$784.82		$881.4301	$881.44	$881.45	$881.40