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	$191.80	7.703%	$206.5744	$206.57	$206.55	$206.60
Purchase #2	$40.48	4.171%	$42.1684	$42.17	$42.15	$42.20
Purchase #3	$54.70	12.564%	$61.5725	$61.57	$61.55	$61.60
Purchase #4	$81.41	11.628%	$90.8764	$90.88	$90.90	$90.90
Purchase #5	$215.60	8.465%	$233.8505	$233.85	$233.85	$233.90
Purchase #6	$13.37	4.132%	$13.9224	$13.92	$13.90	$13.90
Purchase #7	$45.76	12.118%	$51.3052	$51.31	$51.30	$51.30
7 purchase totals =	$643.12		$700.2698	$700.27	$700.20	$700.40