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	$125.88	6.414%	$133.9539	$133.95	$133.95	$134.00
Purchase #2	$189.90	11.391%	$211.5315	$211.53	$211.55	$211.50
Purchase #3	$204.69	4.307%	$213.506	$213.51	$213.50	$213.50
Purchase #4	$88.25	7.469%	$94.8414	$94.84	$94.85	$94.80
Purchase #5	$55.27	7.598%	$59.4694	$59.47	$59.45	$59.50
Purchase #6	$114.58	11.366%	$127.6032	$127.60	$127.60	$127.60
Purchase #7	$24.50	10.695%	$27.1203	$27.12	$27.10	$27.10
7 purchase totals =	$803.07		$868.0257	$868.02	$868.00	$868.00