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	$145.48	3.373%	$150.387	$150.39	$150.40	$150.40
Purchase #2	$97.29	7.624%	$104.7074	$104.71	$104.70	$104.70
Purchase #3	$116.36	6.561%	$123.9944	$123.99	$124.00	$124.00
Purchase #4	$73.95	6.704%	$78.9076	$78.91	$78.90	$78.90
Purchase #5	$64.46	11.825%	$72.0824	$72.08	$72.10	$72.10
Purchase #6	$114.79	7.153%	$123.0009	$123.00	$123.00	$123.00
Purchase #7	$231.28	6.699%	$246.7734	$246.77	$246.75	$246.80
7 purchase totals =	$843.61		$899.8531	$899.85	$899.85	$899.90