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	$105.77	9.638%	$115.9641	$115.96	$115.95	$116.00
Purchase #2	$122.66	4.301%	$127.9356	$127.94	$127.95	$127.90
Purchase #3	$160.41	8.725%	$174.4058	$174.41	$174.40	$174.40
Purchase #4	$79.99	12.334%	$89.856	$89.86	$89.85	$89.90
Purchase #5	$151.39	5.218%	$159.2895	$159.29	$159.30	$159.30
Purchase #6	$242.64	11.648%	$270.9027	$270.90	$270.90	$270.90
Purchase #7	$192.49	13.308%	$218.1066	$218.11	$218.10	$218.10
7 purchase totals =	$1,055.35		$1,156.4603	$1,156.47	$1,156.45	$1,156.50