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	$154.46	8.152%	$167.0516	$167.05	$167.05	$167.10
Purchase #2	$167.51	3.415%	$173.2305	$173.23	$173.25	$173.20
Purchase #3	$182.42	7.642%	$196.3605	$196.36	$196.35	$196.40
Purchase #4	$83.94	7.390%	$90.1432	$90.14	$90.15	$90.10
Purchase #5	$88.90	3.704%	$92.1929	$92.19	$92.20	$92.20
Purchase #6	$205.81	5.678%	$217.4959	$217.50	$217.50	$217.50
Purchase #7	$174.54	6.757%	$186.3337	$186.33	$186.35	$186.30
7 purchase totals =	$1,057.58		$1,122.8083	$1,122.80	$1,122.85	$1,122.80