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	$168.86	12.370%	$189.748	$189.75	$189.75	$189.70
Purchase #2	$125.57	3.426%	$129.872	$129.87	$129.85	$129.90
Purchase #3	$154.80	6.354%	$164.636	$164.64	$164.65	$164.60
Purchase #4	$75.89	10.575%	$83.9154	$83.92	$83.90	$83.90
Purchase #5	$226.57	6.677%	$241.6981	$241.70	$241.70	$241.70
Purchase #6	$83.69	7.475%	$89.9458	$89.95	$89.95	$89.90
Purchase #7	$187.35	12.158%	$210.128	$210.13	$210.15	$210.10
7 purchase totals =	$1,022.73		$1,109.9433	$1,109.96	$1,109.95	$1,109.80