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	$39.46	8.759%	$42.9163	$42.92	$42.90	$42.90
Purchase #2	$206.53	6.159%	$219.2502	$219.25	$219.25	$219.30
Purchase #3	$39.95	11.224%	$44.434	$44.43	$44.45	$44.40
Purchase #4	$219.89	12.393%	$247.141	$247.14	$247.15	$247.10
Purchase #5	$143.83	5.171%	$151.2674	$151.27	$151.25	$151.30
Purchase #6	$73.59	13.158%	$83.273	$83.27	$83.25	$83.30
Purchase #7	$218.31	5.739%	$230.8388	$230.84	$230.85	$230.80
7 purchase totals =	$941.56		$1,019.1207	$1,019.12	$1,019.10	$1,019.10