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	$69.50	12.259%	$78.02	$78.02	$78.00	$78.00
Purchase #2	$42.48	3.320%	$43.8903	$43.89	$43.90	$43.90
Purchase #3	$8.42	10.869%	$9.3352	$9.34	$9.35	$9.30
Purchase #4	$170.83	12.797%	$192.6911	$192.69	$192.70	$192.70
Purchase #5	$159.59	3.743%	$165.5635	$165.56	$165.55	$165.60
Purchase #6	$9.59	12.819%	$10.8193	$10.82	$10.80	$10.80
Purchase #7	$194.76	9.552%	$213.3635	$213.36	$213.35	$213.40
7 purchase totals =	$655.17		$713.6829	$713.68	$713.65	$713.70