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	$25.43	10.532%	$28.1083	$28.11	$28.10	$28.10
Purchase #2	$119.38	5.524%	$125.9746	$125.97	$125.95	$126.00
Purchase #3	$83.75	7.607%	$90.1209	$90.12	$90.10	$90.10
Purchase #4	$139.48	4.538%	$145.8096	$145.81	$145.80	$145.80
Purchase #5	$78.43	10.597%	$86.7412	$86.74	$86.75	$86.70
Purchase #6	$132.67	5.393%	$139.8249	$139.82	$139.80	$139.80
Purchase #7	$96.49	12.541%	$108.5908	$108.59	$108.60	$108.60
7 purchase totals =	$675.63		$725.1703	$725.16	$725.10	$725.10