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	$119.61	9.605%	$131.0985	$131.10	$131.10	$131.10
Purchase #2	$134.44	10.583%	$148.6678	$148.67	$148.65	$148.70
Purchase #3	$162.25	7.791%	$174.8909	$174.89	$174.90	$174.90
Purchase #4	$78.93	9.373%	$86.3281	$86.33	$86.35	$86.30
Purchase #5	$96.90	3.243%	$100.0425	$100.04	$100.05	$100.00
Purchase #6	$150.96	10.854%	$167.3452	$167.35	$167.35	$167.30
Purchase #7	$70.71	4.209%	$73.6862	$73.69	$73.70	$73.70
7 purchase totals =	$813.80		$882.0592	$882.07	$882.10	$882.00