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	$214.99	5.777%	$227.41	$227.41	$227.40	$227.40
Purchase #2	$131.54	3.779%	$136.5109	$136.51	$136.50	$136.50
Purchase #3	$218.40	12.424%	$245.534	$245.53	$245.55	$245.50
Purchase #4	$222.25	13.800%	$252.9205	$252.92	$252.90	$252.90
Purchase #5	$71.45	10.538%	$78.9794	$78.98	$79.00	$79.00
Purchase #6	$16.66	8.743%	$18.1166	$18.12	$18.10	$18.10
Purchase #7	$173.93	6.401%	$185.0633	$185.06	$185.05	$185.10
7 purchase totals =	$1,049.22		$1,144.5347	$1,144.53	$1,144.50	$1,144.50