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	$199.60	12.190%	$223.9312	$223.93	$223.95	$223.90
Purchase #2	$7.68	4.527%	$8.0277	$8.03	$8.05	$8.00
Purchase #3	$197.76	6.732%	$211.0732	$211.07	$211.05	$211.10
Purchase #4	$81.35	8.706%	$88.4323	$88.43	$88.45	$88.40
Purchase #5	$167.59	12.240%	$188.103	$188.10	$188.10	$188.10
Purchase #6	$78.79	13.798%	$89.6614	$89.66	$89.65	$89.70
Purchase #7	$54.96	7.758%	$59.2238	$59.22	$59.20	$59.20
7 purchase totals =	$787.73		$868.4526	$868.44	$868.45	$868.40