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	$163.84	10.776%	$181.4954	$181.50	$181.50	$181.50
Purchase #2	$32.87	8.201%	$35.5657	$35.57	$35.55	$35.60
Purchase #3	$154.88	10.754%	$171.5358	$171.54	$171.55	$171.50
Purchase #4	$53.43	11.384%	$59.5125	$59.51	$59.50	$59.50
Purchase #5	$143.82	10.743%	$159.2706	$159.27	$159.25	$159.30
Purchase #6	$163.69	13.320%	$185.4935	$185.49	$185.50	$185.50
Purchase #7	$29.79	10.555%	$32.9343	$32.93	$32.95	$32.90
7 purchase totals =	$742.32		$825.8078	$825.81	$825.80	$825.80