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	$175.34	12.286%	$196.8823	$196.88	$196.90	$196.90
Purchase #2	$220.98	3.372%	$228.4314	$228.43	$228.45	$228.40
Purchase #3	$211.74	7.383%	$227.3728	$227.37	$227.35	$227.40
Purchase #4	$179.59	4.222%	$187.1723	$187.17	$187.15	$187.20
Purchase #5	$20.87	13.179%	$23.6205	$23.62	$23.60	$23.60
Purchase #6	$76.80	11.785%	$85.8509	$85.85	$85.85	$85.90
Purchase #7	$214.77	8.644%	$233.3347	$233.33	$233.35	$233.30
7 purchase totals =	$1,100.09		$1,182.6649	$1,182.65	$1,182.65	$1,182.70