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	$29.77	13.695%	$33.847	$33.85	$33.85	$33.80
Purchase #2	$75.92	12.618%	$85.4996	$85.50	$85.50	$85.50
Purchase #3	$151.87	9.461%	$166.2384	$166.24	$166.25	$166.20
Purchase #4	$215.38	13.506%	$244.4692	$244.47	$244.45	$244.50
Purchase #5	$249.34	5.391%	$262.7819	$262.78	$262.80	$262.80
Purchase #6	$210.38	5.147%	$221.2083	$221.21	$221.20	$221.20
Purchase #7	$130.82	8.678%	$142.1726	$142.17	$142.15	$142.20
7 purchase totals =	$1,063.48		$1,156.2170	$1,156.22	$1,156.20	$1,156.20