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	$106.25	3.263%	$109.7169	$109.72	$109.70	$109.70
Purchase #2	$131.52	4.819%	$137.8579	$137.86	$137.85	$137.90
Purchase #3	$68.61	7.806%	$73.9657	$73.97	$73.95	$74.00
Purchase #4	$112.36	13.646%	$127.6926	$127.69	$127.70	$127.70
Purchase #5	$213.76	3.337%	$220.8932	$220.89	$220.90	$220.90
Purchase #6	$60.34	12.214%	$67.7099	$67.71	$67.70	$67.70
Purchase #7	$78.54	12.835%	$88.6206	$88.62	$88.60	$88.60
7 purchase totals =	$771.38		$826.4568	$826.46	$826.40	$826.50