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	$57.71	9.129%	$62.9783	$62.98	$63.00	$63.00
Purchase #2	$68.74	6.732%	$73.3676	$73.37	$73.35	$73.40
Purchase #3	$138.69	10.576%	$153.3579	$153.36	$153.35	$153.40
Purchase #4	$144.86	4.166%	$150.8949	$150.89	$150.90	$150.90
Purchase #5	$182.86	11.722%	$204.2948	$204.29	$204.30	$204.30
Purchase #6	$236.49	9.610%	$259.2167	$259.22	$259.20	$259.20
Purchase #7	$90.71	9.157%	$99.0163	$99.02	$99.00	$99.00
7 purchase totals =	$920.06		$1,003.1265	$1,003.13	$1,003.10	$1,003.20