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	$49.69	12.484%	$55.8933	$55.89	$55.90	$55.90
Purchase #2	$66.68	10.757%	$73.8528	$73.85	$73.85	$73.90
Purchase #3	$105.84	5.564%	$111.7289	$111.73	$111.75	$111.70
Purchase #4	$116.48	6.213%	$123.7169	$123.72	$123.70	$123.70
Purchase #5	$209.83	3.124%	$216.3851	$216.39	$216.40	$216.40
Purchase #6	$229.32	3.455%	$237.243	$237.24	$237.25	$237.20
Purchase #7	$242.78	12.754%	$273.7442	$273.74	$273.75	$273.70
7 purchase totals =	$1,020.62		$1,092.5642	$1,092.56	$1,092.60	$1,092.50