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	$37.98	13.351%	$43.0507	$43.05	$43.05	$43.10
Purchase #2	$178.61	6.218%	$189.716	$189.72	$189.70	$189.70
Purchase #3	$76.75	3.578%	$79.4961	$79.50	$79.50	$79.50
Purchase #4	$25.64	9.232%	$28.0071	$28.01	$28.00	$28.00
Purchase #5	$92.27	8.669%	$100.2689	$100.27	$100.25	$100.30
Purchase #6	$92.50	3.788%	$96.0039	$96.00	$96.00	$96.00
Purchase #7	$168.89	11.771%	$188.77	$188.77	$188.75	$188.80
7 purchase totals =	$672.64		$725.3127	$725.32	$725.25	$725.40