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	$158.56	4.359%	$165.4716	$165.47	$165.45	$165.50
Purchase #2	$137.92	11.343%	$153.5643	$153.56	$153.55	$153.60
Purchase #3	$92.68	5.442%	$97.7236	$97.72	$97.70	$97.70
Purchase #4	$83.73	3.224%	$86.4295	$86.43	$86.45	$86.40
Purchase #5	$72.25	5.376%	$76.1342	$76.13	$76.15	$76.10
Purchase #6	$90.34	7.497%	$97.1128	$97.11	$97.10	$97.10
Purchase #7	$162.83	10.314%	$179.6243	$179.62	$179.60	$179.60
7 purchase totals =	$798.31		$856.0603	$856.04	$856.00	$856.00