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	$94.54	11.708%	$105.6087	$105.61	$105.60	$105.60
Purchase #2	$176.47	7.233%	$189.2341	$189.23	$189.25	$189.20
Purchase #3	$154.86	8.728%	$168.3762	$168.38	$168.40	$168.40
Purchase #4	$19.62	7.427%	$21.0772	$21.08	$21.10	$21.10
Purchase #5	$72.71	7.757%	$78.3501	$78.35	$78.35	$78.40
Purchase #6	$114.59	3.788%	$118.9307	$118.93	$118.95	$118.90
Purchase #7	$133.55	3.146%	$137.7515	$137.75	$137.75	$137.80
7 purchase totals =	$766.34		$819.3285	$819.33	$819.40	$819.40