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	$198.39	8.640%	$215.5309	$215.53	$215.55	$215.50
Purchase #2	$57.47	3.391%	$59.4188	$59.42	$59.40	$59.40
Purchase #3	$164.79	4.512%	$172.2253	$172.23	$172.25	$172.20
Purchase #4	$165.76	4.641%	$173.4529	$173.45	$173.45	$173.50
Purchase #5	$111.37	8.388%	$120.7117	$120.71	$120.70	$120.70
Purchase #6	$39.39	6.409%	$41.9145	$41.91	$41.90	$41.90
Purchase #7	$120.60	13.340%	$136.688	$136.69	$136.70	$136.70
7 purchase totals =	$857.77		$919.9421	$919.94	$919.95	$919.90