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	$74.55	10.590%	$82.4448	$82.44	$82.45	$82.40
Purchase #2	$92.47	13.479%	$104.934	$104.93	$104.95	$104.90
Purchase #3	$100.99	8.206%	$109.2772	$109.28	$109.30	$109.30
Purchase #4	$212.82	7.818%	$229.4583	$229.46	$229.45	$229.50
Purchase #5	$133.39	5.127%	$140.2289	$140.23	$140.25	$140.20
Purchase #6	$29.31	11.782%	$32.7633	$32.76	$32.75	$32.80
Purchase #7	$26.40	5.208%	$27.7749	$27.77	$27.75	$27.80
7 purchase totals =	$669.93		$726.8814	$726.87	$726.90	$726.90