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	$57.62	10.786%	$63.8349	$63.83	$63.85	$63.80
Purchase #2	$101.38	10.791%	$112.3199	$112.32	$112.30	$112.30
Purchase #3	$236.77	3.185%	$244.3111	$244.31	$244.30	$244.30
Purchase #4	$207.74	6.526%	$221.2971	$221.30	$221.30	$221.30
Purchase #5	$12.41	5.855%	$13.1366	$13.14	$13.15	$13.10
Purchase #6	$57.44	4.157%	$59.8278	$59.83	$59.85	$59.80
Purchase #7	$146.87	12.281%	$164.9071	$164.91	$164.90	$164.90
7 purchase totals =	$820.23		$879.6345	$879.64	$879.65	$879.50