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	$152.31	3.662%	$157.8876	$157.89	$157.90	$157.90
Purchase #2	$18.83	3.712%	$19.529	$19.53	$19.55	$19.50
Purchase #3	$101.94	3.693%	$105.7046	$105.70	$105.70	$105.70
Purchase #4	$68.47	4.497%	$71.5491	$71.55	$71.55	$71.50
Purchase #5	$219.53	13.173%	$248.4487	$248.45	$248.45	$248.40
Purchase #6	$246.59	11.166%	$274.1242	$274.12	$274.10	$274.10
Purchase #7	$5.33	4.732%	$5.5822	$5.58	$5.60	$5.60
7 purchase totals =	$813.00		$882.8254	$882.82	$882.85	$882.70