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	$100.32	9.102%	$109.4511	$109.45	$109.45	$109.50
Purchase #2	$99.55	5.237%	$104.7634	$104.76	$104.75	$104.80
Purchase #3	$227.84	6.744%	$243.2055	$243.21	$243.20	$243.20
Purchase #4	$93.46	10.873%	$103.6219	$103.62	$103.60	$103.60
Purchase #5	$39.56	4.309%	$41.2646	$41.26	$41.25	$41.30
Purchase #6	$158.37	12.469%	$178.1172	$178.12	$178.10	$178.10
Purchase #7	$215.87	9.346%	$236.0452	$236.05	$236.05	$236.00
7 purchase totals =	$934.97		$1,016.4689	$1,016.47	$1,016.40	$1,016.50