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	$163.63	9.335%	$178.9049	$178.90	$178.90	$178.90
Purchase #2	$222.37	7.237%	$238.4629	$238.46	$238.45	$238.50
Purchase #3	$67.32	7.861%	$72.612	$72.61	$72.60	$72.60
Purchase #4	$98.29	5.605%	$103.7992	$103.80	$103.80	$103.80
Purchase #5	$55.47	3.211%	$57.2511	$57.25	$57.25	$57.30
Purchase #6	$164.46	12.424%	$184.8925	$184.89	$184.90	$184.90
Purchase #7	$84.60	4.214%	$88.165	$88.17	$88.15	$88.20
7 purchase totals =	$856.14		$924.0876	$924.08	$924.05	$924.20