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	$53.65	10.408%	$59.2339	$59.23	$59.25	$59.20
Purchase #2	$40.95	11.434%	$45.6322	$45.63	$45.65	$45.60
Purchase #3	$32.60	11.604%	$36.3829	$36.38	$36.40	$36.40
Purchase #4	$86.78	12.424%	$97.5615	$97.56	$97.55	$97.60
Purchase #5	$83.99	9.649%	$92.0942	$92.09	$92.10	$92.10
Purchase #6	$124.61	4.695%	$130.4604	$130.46	$130.45	$130.50
Purchase #7	$243.31	5.322%	$256.259	$256.26	$256.25	$256.30
7 purchase totals =	$665.89		$717.6241	$717.61	$717.65	$717.70