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	$148.45	10.548%	$164.1085	$164.11	$164.10	$164.10
Purchase #2	$196.27	8.364%	$212.686	$212.69	$212.70	$212.70
Purchase #3	$229.87	10.128%	$253.1512	$253.15	$253.15	$253.20
Purchase #4	$22.40	10.264%	$24.6991	$24.70	$24.70	$24.70
Purchase #5	$112.39	13.246%	$127.2772	$127.28	$127.30	$127.30
Purchase #6	$203.76	8.681%	$221.4484	$221.45	$221.45	$221.40
Purchase #7	$109.71	12.554%	$123.483	$123.48	$123.50	$123.50
7 purchase totals =	$1,022.85		$1,126.8534	$1,126.86	$1,126.90	$1,126.90