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	$38.55	13.641%	$43.8086	$43.81	$43.80	$43.80
Purchase #2	$10.73	7.355%	$11.5192	$11.52	$11.50	$11.50
Purchase #3	$230.61	6.646%	$245.9363	$245.94	$245.95	$245.90
Purchase #4	$236.79	9.601%	$259.5242	$259.52	$259.50	$259.50
Purchase #5	$223.98	4.191%	$233.367	$233.37	$233.35	$233.40
Purchase #6	$33.83	4.679%	$35.4129	$35.41	$35.40	$35.40
Purchase #7	$39.45	6.285%	$41.9294	$41.93	$41.95	$41.90
7 purchase totals =	$813.94		$871.4976	$871.50	$871.45	$871.40