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	$224.73	6.811%	$240.0364	$240.04	$240.05	$240.00
Purchase #2	$197.93	12.465%	$222.602	$222.60	$222.60	$222.60
Purchase #3	$191.81	13.411%	$217.5336	$217.53	$217.55	$217.50
Purchase #4	$96.93	7.679%	$104.3733	$104.37	$104.35	$104.40
Purchase #5	$77.57	7.353%	$83.2737	$83.27	$83.25	$83.30
Purchase #6	$89.71	6.223%	$95.2927	$95.29	$95.30	$95.30
Purchase #7	$129.25	12.532%	$145.4476	$145.45	$145.45	$145.40
7 purchase totals =	$1,007.93		$1,108.5593	$1,108.55	$1,108.55	$1,108.50