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	$63.87	11.727%	$71.36	$71.36	$71.35	$71.40
Purchase #2	$56.85	4.635%	$59.485	$59.49	$59.50	$59.50
Purchase #3	$195.85	13.469%	$222.229	$222.23	$222.25	$222.20
Purchase #4	$170.83	11.786%	$190.964	$190.96	$190.95	$191.00
Purchase #5	$61.52	3.351%	$63.5815	$63.58	$63.60	$63.60
Purchase #6	$218.37	5.524%	$230.4328	$230.43	$230.45	$230.40
Purchase #7	$84.48	10.568%	$93.4078	$93.41	$93.40	$93.40
7 purchase totals =	$851.77		$931.4601	$931.46	$931.50	$931.50