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	$112.88	5.140%	$118.682	$118.68	$118.70	$118.70
Purchase #2	$33.72	12.338%	$37.8804	$37.88	$37.90	$37.90
Purchase #3	$122.47	10.543%	$135.382	$135.38	$135.40	$135.40
Purchase #4	$130.48	12.597%	$146.9166	$146.92	$146.90	$146.90
Purchase #5	$161.41	6.646%	$172.1373	$172.14	$172.15	$172.10
Purchase #6	$247.56	4.762%	$259.3488	$259.35	$259.35	$259.30
Purchase #7	$136.84	7.118%	$146.5803	$146.58	$146.60	$146.60
7 purchase totals =	$945.36		$1,016.9274	$1,016.93	$1,017.00	$1,016.90