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	$43.52	4.694%	$45.5628	$45.56	$45.55	$45.60
Purchase #2	$233.89	10.821%	$259.1992	$259.20	$259.20	$259.20
Purchase #3	$18.59	11.680%	$20.7613	$20.76	$20.75	$20.80
Purchase #4	$151.59	5.565%	$160.026	$160.03	$160.05	$160.00
Purchase #5	$47.93	6.321%	$50.9597	$50.96	$50.95	$51.00
Purchase #6	$31.80	12.274%	$35.7031	$35.70	$35.70	$35.70
Purchase #7	$86.93	11.155%	$96.627	$96.63	$96.65	$96.60
7 purchase totals =	$614.25		$668.8391	$668.84	$668.85	$668.90