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	$190.51	5.384%	$200.7671	$200.77	$200.75	$200.80
Purchase #2	$109.51	13.639%	$124.4461	$124.45	$124.45	$124.40
Purchase #3	$163.86	3.524%	$169.6344	$169.63	$169.65	$169.60
Purchase #4	$19.49	4.381%	$20.3439	$20.34	$20.35	$20.30
Purchase #5	$55.82	6.445%	$59.4176	$59.42	$59.40	$59.40
Purchase #6	$159.29	12.741%	$179.5851	$179.59	$179.60	$179.60
Purchase #7	$118.49	7.683%	$127.5936	$127.59	$127.60	$127.60
7 purchase totals =	$816.97		$881.7878	$881.79	$881.80	$881.70