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	$66.69	7.166%	$71.469	$71.47	$71.45	$71.50
Purchase #2	$224.29	3.172%	$231.4045	$231.40	$231.40	$231.40
Purchase #3	$56.48	5.432%	$59.548	$59.55	$59.55	$59.50
Purchase #4	$117.82	12.729%	$132.8173	$132.82	$132.80	$132.80
Purchase #5	$170.25	4.650%	$178.1666	$178.17	$178.15	$178.20
Purchase #6	$53.30	12.370%	$59.8932	$59.89	$59.90	$59.90
Purchase #7	$144.76	12.346%	$162.6321	$162.63	$162.65	$162.60
7 purchase totals =	$833.59		$895.9307	$895.93	$895.90	$895.90