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	$6.33	10.789%	$7.0129	$7.01	$7.00	$7.00
Purchase #2	$62.77	3.516%	$64.977	$64.98	$65.00	$65.00
Purchase #3	$162.39	4.708%	$170.0353	$170.04	$170.05	$170.00
Purchase #4	$48.90	12.805%	$55.1616	$55.16	$55.15	$55.20
Purchase #5	$127.51	11.546%	$142.2323	$142.23	$142.25	$142.20
Purchase #6	$166.69	5.351%	$175.6096	$175.61	$175.60	$175.60
Purchase #7	$136.59	7.278%	$146.531	$146.53	$146.55	$146.50
7 purchase totals =	$711.18		$761.5597	$761.56	$761.60	$761.50