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	$63.49	6.635%	$67.7026	$67.70	$67.70	$67.70
Purchase #2	$199.98	13.683%	$227.3433	$227.34	$227.35	$227.30
Purchase #3	$174.56	6.369%	$185.6777	$185.68	$185.70	$185.70
Purchase #4	$104.58	13.662%	$118.8677	$118.87	$118.85	$118.90
Purchase #5	$80.96	3.456%	$83.758	$83.76	$83.75	$83.80
Purchase #6	$245.46	8.148%	$265.4601	$265.46	$265.45	$265.50
Purchase #7	$68.54	13.184%	$77.5763	$77.58	$77.60	$77.60
7 purchase totals =	$937.57		$1,026.3857	$1,026.39	$1,026.40	$1,026.50