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	$70.36	8.514%	$76.3505	$76.35	$76.35	$76.40
Purchase #2	$210.61	7.698%	$226.8228	$226.82	$226.80	$226.80
Purchase #3	$233.27	12.370%	$262.1255	$262.13	$262.15	$262.10
Purchase #4	$39.66	8.190%	$42.9082	$42.91	$42.90	$42.90
Purchase #5	$205.85	8.294%	$222.9232	$222.92	$222.90	$222.90
Purchase #6	$78.99	13.498%	$89.6521	$89.65	$89.65	$89.70
Purchase #7	$226.43	8.811%	$246.3807	$246.38	$246.40	$246.40
7 purchase totals =	$1,065.17		$1,167.1630	$1,167.16	$1,167.15	$1,167.20