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	$33.73	4.546%	$35.2634	$35.26	$35.25	$35.30
Purchase #2	$17.61	3.602%	$18.2443	$18.24	$18.25	$18.20
Purchase #3	$46.42	10.855%	$51.4589	$51.46	$51.45	$51.50
Purchase #4	$49.34	4.286%	$51.4547	$51.45	$51.45	$51.50
Purchase #5	$212.59	4.667%	$222.5116	$222.51	$222.50	$222.50
Purchase #6	$72.58	10.565%	$80.2481	$80.25	$80.25	$80.20
Purchase #7	$163.44	4.724%	$171.1609	$171.16	$171.15	$171.20
7 purchase totals =	$595.71		$630.3419	$630.33	$630.30	$630.40