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	$33.56	6.466%	$35.73	$35.73	$35.75	$35.70
Purchase #2	$125.46	12.804%	$141.5239	$141.52	$141.50	$141.50
Purchase #3	$189.61	4.545%	$198.2278	$198.23	$198.25	$198.20
Purchase #4	$39.56	10.402%	$43.675	$43.68	$43.70	$43.70
Purchase #5	$143.48	11.770%	$160.3676	$160.37	$160.35	$160.40
Purchase #6	$190.51	5.236%	$200.4851	$200.49	$200.50	$200.50
Purchase #7	$167.42	8.811%	$182.1714	$182.17	$182.15	$182.20
7 purchase totals =	$889.60		$962.1808	$962.19	$962.20	$962.20