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	$31.86	6.742%	$34.008	$34.01	$34.00	$34.00
Purchase #2	$128.89	11.194%	$143.3179	$143.32	$143.30	$143.30
Purchase #3	$180.55	13.217%	$204.4133	$204.41	$204.40	$204.40
Purchase #4	$58.37	11.799%	$65.2571	$65.26	$65.25	$65.30
Purchase #5	$215.69	12.616%	$242.9015	$242.90	$242.90	$242.90
Purchase #6	$196.65	11.511%	$219.2864	$219.29	$219.30	$219.30
Purchase #7	$111.39	10.714%	$123.3243	$123.32	$123.30	$123.30
7 purchase totals =	$923.40		$1,032.5085	$1,032.51	$1,032.45	$1,032.50