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	$14.96	13.300%	$16.9497	$16.95	$16.95	$16.90
Purchase #2	$8.69	13.460%	$9.8597	$9.86	$9.85	$9.90
Purchase #3	$131.33	7.846%	$141.6342	$141.63	$141.65	$141.60
Purchase #4	$5.61	13.139%	$6.3471	$6.35	$6.35	$6.30
Purchase #5	$137.56	12.188%	$154.3258	$154.33	$154.35	$154.30
Purchase #6	$144.51	11.178%	$160.6633	$160.66	$160.65	$160.70
Purchase #7	$92.87	13.646%	$105.543	$105.54	$105.55	$105.50
7 purchase totals =	$535.53		$595.3228	$595.32	$595.35	$595.20