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	$154.27	8.260%	$167.0127	$167.01	$167.00	$167.00
Purchase #2	$128.43	9.152%	$140.1839	$140.18	$140.20	$140.20
Purchase #3	$19.64	3.493%	$20.326	$20.33	$20.35	$20.30
Purchase #4	$210.42	3.859%	$218.5401	$218.54	$218.55	$218.50
Purchase #5	$111.46	6.229%	$118.4028	$118.40	$118.40	$118.40
Purchase #6	$165.40	4.405%	$172.6859	$172.69	$172.70	$172.70
Purchase #7	$171.29	12.499%	$192.6995	$192.70	$192.70	$192.70
7 purchase totals =	$960.91		$1,029.8509	$1,029.85	$1,029.90	$1,029.80