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	$39.92	3.806%	$41.4394	$41.44	$41.45	$41.40
Purchase #2	$109.63	13.798%	$124.7567	$124.76	$124.75	$124.80
Purchase #3	$160.79	6.711%	$171.5806	$171.58	$171.60	$171.60
Purchase #4	$201.31	10.633%	$222.7153	$222.72	$222.70	$222.70
Purchase #5	$149.81	11.499%	$167.0367	$167.04	$167.05	$167.00
Purchase #6	$215.26	5.610%	$227.3361	$227.34	$227.35	$227.30
Purchase #7	$53.77	13.685%	$61.1284	$61.13	$61.15	$61.10
7 purchase totals =	$930.49		$1,015.9932	$1,016.01	$1,016.05	$1,015.90