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	$204.46	9.486%	$223.8551	$223.86	$223.85	$223.90
Purchase #2	$235.43	12.608%	$265.113	$265.11	$265.10	$265.10
Purchase #3	$225.39	12.854%	$254.3616	$254.36	$254.35	$254.40
Purchase #4	$82.99	12.516%	$93.377	$93.38	$93.40	$93.40
Purchase #5	$205.91	6.622%	$219.5454	$219.55	$219.55	$219.50
Purchase #6	$167.26	3.747%	$173.5272	$173.53	$173.55	$173.50
Purchase #7	$73.34	7.272%	$78.6733	$78.67	$78.65	$78.70
7 purchase totals =	$1,194.78		$1,308.4526	$1,308.46	$1,308.45	$1,308.50