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	$76.86	7.799%	$82.8543	$82.85	$82.85	$82.90
Purchase #2	$238.58	8.395%	$258.6088	$258.61	$258.60	$258.60
Purchase #3	$122.78	5.525%	$129.5636	$129.56	$129.55	$129.60
Purchase #4	$54.59	13.371%	$61.8892	$61.89	$61.90	$61.90
Purchase #5	$12.70	12.515%	$14.2894	$14.29	$14.30	$14.30
Purchase #6	$7.48	6.377%	$7.957	$7.96	$7.95	$8.00
Purchase #7	$162.85	7.259%	$174.6713	$174.67	$174.65	$174.70
7 purchase totals =	$675.84		$729.8336	$729.83	$729.80	$730.00