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	$67.47	7.796%	$72.73	$72.73	$72.75	$72.70
Purchase #2	$213.80	4.350%	$223.1003	$223.10	$223.10	$223.10
Purchase #3	$41.42	12.103%	$46.4331	$46.43	$46.45	$46.40
Purchase #4	$72.44	6.457%	$77.1175	$77.12	$77.10	$77.10
Purchase #5	$153.64	4.386%	$160.3787	$160.38	$160.40	$160.40
Purchase #6	$238.60	10.498%	$263.6482	$263.65	$263.65	$263.60
Purchase #7	$94.53	10.518%	$104.4727	$104.47	$104.45	$104.50
7 purchase totals =	$881.90		$947.8805	$947.88	$947.90	$947.80