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	$222.85	10.164%	$245.5005	$245.50	$245.50	$245.50
Purchase #2	$53.50	10.351%	$59.0378	$59.04	$59.05	$59.00
Purchase #3	$81.46	9.659%	$89.3282	$89.33	$89.35	$89.30
Purchase #4	$153.28	4.105%	$159.5721	$159.57	$159.55	$159.60
Purchase #5	$186.53	4.152%	$194.2747	$194.27	$194.25	$194.30
Purchase #6	$121.99	7.560%	$131.2124	$131.21	$131.20	$131.20
Purchase #7	$13.68	12.185%	$15.3469	$15.35	$15.35	$15.30
7 purchase totals =	$833.29		$894.2726	$894.27	$894.25	$894.20