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	$204.36	10.809%	$226.4493	$226.45	$226.45	$226.40
Purchase #2	$104.39	4.866%	$109.4696	$109.47	$109.45	$109.50
Purchase #3	$135.52	12.281%	$152.1632	$152.16	$152.15	$152.20
Purchase #4	$146.89	10.452%	$162.2429	$162.24	$162.25	$162.20
Purchase #5	$50.50	8.679%	$54.8829	$54.88	$54.90	$54.90
Purchase #6	$14.85	4.652%	$15.5408	$15.54	$15.55	$15.50
Purchase #7	$37.84	8.264%	$40.9671	$40.97	$40.95	$41.00
7 purchase totals =	$694.35		$761.7158	$761.71	$761.70	$761.70