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	$150.66	5.332%	$158.6932	$158.69	$158.70	$158.70
Purchase #2	$71.67	8.817%	$77.9891	$77.99	$78.00	$78.00
Purchase #3	$140.81	9.678%	$154.4376	$154.44	$154.45	$154.40
Purchase #4	$222.90	4.280%	$232.4401	$232.44	$232.45	$232.40
Purchase #5	$99.63	5.579%	$105.1884	$105.19	$105.20	$105.20
Purchase #6	$200.87	11.228%	$223.4237	$223.42	$223.40	$223.40
Purchase #7	$127.35	10.271%	$140.4301	$140.43	$140.45	$140.40
7 purchase totals =	$1,013.89		$1,092.6022	$1,092.60	$1,092.65	$1,092.50