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	$46.89	11.579%	$52.3194	$52.32	$52.30	$52.30
Purchase #2	$164.58	5.472%	$173.5858	$173.59	$173.60	$173.60
Purchase #3	$77.99	13.294%	$88.358	$88.36	$88.35	$88.40
Purchase #4	$127.79	4.699%	$133.7949	$133.79	$133.80	$133.80
Purchase #5	$223.60	6.165%	$237.3849	$237.38	$237.40	$237.40
Purchase #6	$181.65	12.310%	$204.0111	$204.01	$204.00	$204.00
Purchase #7	$116.36	5.824%	$123.1368	$123.14	$123.15	$123.10
7 purchase totals =	$938.86		$1,012.5909	$1,012.59	$1,012.60	$1,012.60