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	$193.40	11.346%	$215.3432	$215.34	$215.35	$215.30
Purchase #2	$10.66	12.457%	$11.9879	$11.99	$12.00	$12.00
Purchase #3	$69.62	12.711%	$78.4694	$78.47	$78.45	$78.50
Purchase #4	$18.81	8.270%	$20.3656	$20.37	$20.35	$20.40
Purchase #5	$237.29	11.500%	$264.5784	$264.58	$264.60	$264.60
Purchase #6	$66.73	8.462%	$72.3767	$72.38	$72.40	$72.40
Purchase #7	$208.40	11.146%	$231.6283	$231.63	$231.65	$231.60
7 purchase totals =	$804.91		$894.7495	$894.76	$894.80	$894.80