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	$52.43	8.345%	$56.8053	$56.81	$56.80	$56.80
Purchase #2	$29.33	8.377%	$31.787	$31.79	$31.80	$31.80
Purchase #3	$99.53	3.838%	$103.35	$103.35	$103.35	$103.40
Purchase #4	$100.52	10.469%	$111.0434	$111.04	$111.05	$111.00
Purchase #5	$15.31	6.103%	$16.2444	$16.24	$16.25	$16.20
Purchase #6	$182.84	7.234%	$196.0666	$196.07	$196.05	$196.10
Purchase #7	$207.40	5.531%	$218.8713	$218.87	$218.85	$218.90
7 purchase totals =	$687.36		$734.1680	$734.17	$734.15	$734.20