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	$118.99	10.275%	$131.2162	$131.22	$131.20	$131.20
Purchase #2	$133.71	8.386%	$144.9229	$144.92	$144.90	$144.90
Purchase #3	$142.57	6.537%	$151.8898	$151.89	$151.90	$151.90
Purchase #4	$32.35	4.867%	$33.9245	$33.92	$33.90	$33.90
Purchase #5	$88.84	8.568%	$96.4518	$96.45	$96.45	$96.50
Purchase #6	$215.81	8.414%	$233.9683	$233.97	$233.95	$234.00
Purchase #7	$24.81	9.113%	$27.0709	$27.07	$27.05	$27.10
7 purchase totals =	$757.08		$819.4444	$819.44	$819.35	$819.50