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	$209.36	11.730%	$233.9179	$233.92	$233.90	$233.90
Purchase #2	$19.40	10.268%	$21.392	$21.39	$21.40	$21.40
Purchase #3	$40.99	3.551%	$42.4456	$42.45	$42.45	$42.40
Purchase #4	$105.48	13.681%	$119.9107	$119.91	$119.90	$119.90
Purchase #5	$163.50	3.240%	$168.7974	$168.80	$168.80	$168.80
Purchase #6	$206.36	10.452%	$227.9287	$227.93	$227.95	$227.90
Purchase #7	$193.75	5.717%	$204.8267	$204.83	$204.85	$204.80
7 purchase totals =	$938.84		$1,019.2190	$1,019.23	$1,019.25	$1,019.10