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	$22.43	7.476%	$24.1069	$24.11	$24.10	$24.10
Purchase #2	$201.39	12.816%	$227.2001	$227.20	$227.20	$227.20
Purchase #3	$248.53	6.184%	$263.8991	$263.90	$263.90	$263.90
Purchase #4	$115.44	10.161%	$127.1699	$127.17	$127.15	$127.20
Purchase #5	$92.56	9.745%	$101.58	$101.58	$101.60	$101.60
Purchase #6	$141.57	7.735%	$152.5204	$152.52	$152.50	$152.50
Purchase #7	$117.77	10.437%	$130.0617	$130.06	$130.05	$130.10
7 purchase totals =	$939.69		$1,026.5381	$1,026.54	$1,026.50	$1,026.60