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	$156.97	6.647%	$167.4038	$167.40	$167.40	$167.40
Purchase #2	$155.35	12.347%	$174.5311	$174.53	$174.55	$174.50
Purchase #3	$6.30	11.436%	$7.0205	$7.02	$7.00	$7.00
Purchase #4	$212.33	4.634%	$222.1694	$222.17	$222.15	$222.20
Purchase #5	$205.62	7.740%	$221.535	$221.54	$221.55	$221.50
Purchase #6	$76.93	7.390%	$82.6151	$82.62	$82.60	$82.60
Purchase #7	$65.61	10.500%	$72.4991	$72.50	$72.50	$72.50
7 purchase totals =	$879.11		$947.7740	$947.78	$947.75	$947.70