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	$43.78	6.362%	$46.5653	$46.57	$46.55	$46.60
Purchase #2	$85.88	5.376%	$90.4969	$90.50	$90.50	$90.50
Purchase #3	$176.90	7.395%	$189.9818	$189.98	$190.00	$190.00
Purchase #4	$135.72	12.422%	$152.5791	$152.58	$152.60	$152.60
Purchase #5	$173.41	13.224%	$196.3417	$196.34	$196.35	$196.30
Purchase #6	$103.89	4.545%	$108.6118	$108.61	$108.60	$108.60
Purchase #7	$73.53	3.121%	$75.8249	$75.82	$75.80	$75.80
7 purchase totals =	$793.11		$860.4015	$860.40	$860.40	$860.40