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	$147.98	6.508%	$157.6105	$157.61	$157.60	$157.60
Purchase #2	$172.36	9.102%	$188.0482	$188.05	$188.05	$188.00
Purchase #3	$54.59	9.515%	$59.7842	$59.78	$59.80	$59.80
Purchase #4	$128.47	10.351%	$141.7679	$141.77	$141.75	$141.80
Purchase #5	$132.31	13.836%	$150.6164	$150.62	$150.60	$150.60
Purchase #6	$113.42	13.740%	$129.0039	$129.00	$129.00	$129.00
Purchase #7	$206.28	13.116%	$233.3357	$233.34	$233.35	$233.30
7 purchase totals =	$955.41		$1,060.1668	$1,060.17	$1,060.15	$1,060.10