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	$192.94	10.457%	$213.1157	$213.12	$213.10	$213.10
Purchase #2	$161.46	11.336%	$179.7631	$179.76	$179.75	$179.80
Purchase #3	$47.41	11.424%	$52.8261	$52.83	$52.85	$52.80
Purchase #4	$36.43	9.830%	$40.0111	$40.01	$40.00	$40.00
Purchase #5	$56.57	5.447%	$59.6514	$59.65	$59.65	$59.70
Purchase #6	$29.49	11.273%	$32.8144	$32.81	$32.80	$32.80
Purchase #7	$184.94	8.651%	$200.9392	$200.94	$200.95	$200.90
7 purchase totals =	$709.24		$779.1210	$779.12	$779.10	$779.10