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	$218.36	3.706%	$226.4524	$226.45	$226.45	$226.50
Purchase #2	$104.45	5.137%	$109.8156	$109.82	$109.80	$109.80
Purchase #3	$77.51	4.792%	$81.2243	$81.22	$81.20	$81.20
Purchase #4	$139.45	12.425%	$156.7767	$156.78	$156.80	$156.80
Purchase #5	$158.85	7.497%	$170.759	$170.76	$170.75	$170.80
Purchase #6	$30.26	3.511%	$31.3224	$31.32	$31.30	$31.30
Purchase #7	$222.54	4.186%	$231.8555	$231.86	$231.85	$231.90
7 purchase totals =	$951.42		$1,008.2059	$1,008.21	$1,008.15	$1,008.30