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	$215.36	3.230%	$222.3161	$222.32	$222.30	$222.30
Purchase #2	$242.97	10.822%	$269.2642	$269.26	$269.25	$269.30
Purchase #3	$182.79	6.327%	$194.3551	$194.36	$194.35	$194.40
Purchase #4	$157.31	6.729%	$167.8954	$167.90	$167.90	$167.90
Purchase #5	$131.87	5.466%	$139.078	$139.08	$139.10	$139.10
Purchase #6	$131.45	9.501%	$143.9391	$143.94	$143.95	$143.90
Purchase #7	$31.55	13.103%	$35.684	$35.68	$35.70	$35.70
7 purchase totals =	$1,093.30		$1,172.5319	$1,172.54	$1,172.55	$1,172.60