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	$169.86	7.495%	$182.591	$182.59	$182.60	$182.60
Purchase #2	$50.47	6.114%	$53.5557	$53.56	$53.55	$53.60
Purchase #3	$202.55	4.209%	$211.0753	$211.08	$211.10	$211.10
Purchase #4	$92.28	3.136%	$95.1739	$95.17	$95.15	$95.20
Purchase #5	$56.63	5.104%	$59.5204	$59.52	$59.50	$59.50
Purchase #6	$196.37	3.569%	$203.3784	$203.38	$203.40	$203.40
Purchase #7	$138.27	8.837%	$150.4889	$150.49	$150.50	$150.50
7 purchase totals =	$906.43		$955.7836	$955.79	$955.80	$955.90