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	$107.82	5.729%	$113.997	$114.00	$114.00	$114.00
Purchase #2	$223.76	7.178%	$239.8215	$239.82	$239.80	$239.80
Purchase #3	$214.83	8.610%	$233.3269	$233.33	$233.35	$233.30
Purchase #4	$103.44	12.519%	$116.3897	$116.39	$116.40	$116.40
Purchase #5	$97.35	12.779%	$109.7904	$109.79	$109.80	$109.80
Purchase #6	$94.95	9.429%	$103.9028	$103.90	$103.90	$103.90
Purchase #7	$33.61	6.588%	$35.8242	$35.82	$35.80	$35.80
7 purchase totals =	$875.76		$953.0525	$953.05	$953.05	$953.00