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	$151.73	10.229%	$167.2505	$167.25	$167.25	$167.30
Purchase #2	$10.61	4.473%	$11.0846	$11.08	$11.10	$11.10
Purchase #3	$106.53	3.648%	$110.4162	$110.42	$110.40	$110.40
Purchase #4	$19.89	8.460%	$21.5727	$21.57	$21.55	$21.60
Purchase #5	$211.47	4.668%	$221.3414	$221.34	$221.35	$221.30
Purchase #6	$147.35	3.716%	$152.8255	$152.83	$152.85	$152.80
Purchase #7	$125.70	9.648%	$137.8275	$137.83	$137.85	$137.80
7 purchase totals =	$773.28		$822.3184	$822.32	$822.35	$822.30