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	$184.81	6.554%	$196.9224	$196.92	$196.90	$196.90
Purchase #2	$81.79	12.388%	$91.9221	$91.92	$91.90	$91.90
Purchase #3	$218.27	9.381%	$238.7459	$238.75	$238.75	$238.70
Purchase #4	$121.69	4.716%	$127.4289	$127.43	$127.45	$127.40
Purchase #5	$224.80	9.619%	$246.4235	$246.42	$246.40	$246.40
Purchase #6	$29.80	7.494%	$32.0332	$32.03	$32.05	$32.00
Purchase #7	$185.47	3.420%	$191.8131	$191.81	$191.80	$191.80
7 purchase totals =	$1,046.63		$1,125.2891	$1,125.28	$1,125.25	$1,125.10