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	$215.93	6.769%	$230.5463	$230.55	$230.55	$230.50
Purchase #2	$35.31	5.858%	$37.3785	$37.38	$37.40	$37.40
Purchase #3	$127.46	5.829%	$134.8896	$134.89	$134.90	$134.90
Purchase #4	$7.48	6.145%	$7.9396	$7.94	$7.95	$7.90
Purchase #5	$217.38	5.737%	$229.8511	$229.85	$229.85	$229.90
Purchase #6	$29.48	13.199%	$33.3711	$33.37	$33.35	$33.40
Purchase #7	$31.99	3.117%	$32.9871	$32.99	$33.00	$33.00
7 purchase totals =	$665.03		$706.9633	$706.97	$707.00	$707.00