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	$239.59	8.337%	$259.5646	$259.56	$259.55	$259.60
Purchase #2	$37.39	13.288%	$42.3584	$42.36	$42.35	$42.40
Purchase #3	$13.25	10.432%	$14.6322	$14.63	$14.65	$14.60
Purchase #4	$17.45	4.452%	$18.2269	$18.23	$18.25	$18.20
Purchase #5	$152.83	12.821%	$172.4243	$172.42	$172.40	$172.40
Purchase #6	$186.31	11.165%	$207.1115	$207.11	$207.10	$207.10
Purchase #7	$91.80	8.855%	$99.9289	$99.93	$99.95	$99.90
7 purchase totals =	$738.62		$814.2468	$814.24	$814.25	$814.20