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	$79.98	10.693%	$88.5323	$88.53	$88.55	$88.50
Purchase #2	$210.87	7.686%	$227.0775	$227.08	$227.10	$227.10
Purchase #3	$163.51	11.695%	$182.6325	$182.63	$182.65	$182.60
Purchase #4	$31.88	7.613%	$34.307	$34.31	$34.30	$34.30
Purchase #5	$57.98	3.343%	$59.9183	$59.92	$59.90	$59.90
Purchase #6	$247.73	13.164%	$280.3412	$280.34	$280.35	$280.30
Purchase #7	$137.66	11.820%	$153.9314	$153.93	$153.95	$153.90
7 purchase totals =	$929.61		$1,026.7402	$1,026.74	$1,026.80	$1,026.60