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	$118.64	7.168%	$127.1441	$127.14	$127.15	$127.10
Purchase #2	$217.45	6.718%	$232.0583	$232.06	$232.05	$232.10
Purchase #3	$173.43	9.143%	$189.2867	$189.29	$189.30	$189.30
Purchase #4	$85.83	4.810%	$89.9584	$89.96	$89.95	$90.00
Purchase #5	$113.78	3.615%	$117.8931	$117.89	$117.90	$117.90
Purchase #6	$112.35	4.384%	$117.2754	$117.28	$117.30	$117.30
Purchase #7	$218.69	12.135%	$245.228	$245.23	$245.25	$245.20
7 purchase totals =	$1,040.17		$1,118.8440	$1,118.85	$1,118.90	$1,118.90