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	$166.71	8.791%	$181.3655	$181.37	$181.35	$181.40
Purchase #2	$17.69	4.592%	$18.5023	$18.50	$18.50	$18.50
Purchase #3	$66.99	8.772%	$72.8664	$72.87	$72.85	$72.90
Purchase #4	$68.66	4.528%	$71.7689	$71.77	$71.75	$71.80
Purchase #5	$150.47	4.180%	$156.7596	$156.76	$156.75	$156.80
Purchase #6	$41.89	6.117%	$44.4524	$44.45	$44.45	$44.50
Purchase #7	$62.98	9.329%	$68.8554	$68.86	$68.85	$68.90
7 purchase totals =	$575.39		$614.5705	$614.58	$614.50	$614.80