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	$176.99	12.703%	$199.473	$199.47	$199.45	$199.50
Purchase #2	$246.75	7.340%	$264.8615	$264.86	$264.85	$264.90
Purchase #3	$145.84	3.478%	$150.9123	$150.91	$150.90	$150.90
Purchase #4	$90.57	13.130%	$102.4618	$102.46	$102.45	$102.50
Purchase #5	$61.52	6.136%	$65.2949	$65.29	$65.30	$65.30
Purchase #6	$106.98	5.744%	$113.1249	$113.12	$113.10	$113.10
Purchase #7	$112.78	7.506%	$121.2453	$121.25	$121.25	$121.20
7 purchase totals =	$941.43		$1,017.3737	$1,017.36	$1,017.30	$1,017.40