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	$42.31	9.322%	$46.2541	$46.25	$46.25	$46.30
Purchase #2	$67.53	12.760%	$76.1468	$76.15	$76.15	$76.10
Purchase #3	$129.59	8.268%	$140.3045	$140.30	$140.30	$140.30
Purchase #4	$100.49	12.253%	$112.803	$112.80	$112.80	$112.80
Purchase #5	$41.96	6.778%	$44.804	$44.80	$44.80	$44.80
Purchase #6	$90.98	5.384%	$95.8784	$95.88	$95.90	$95.90
Purchase #7	$144.69	9.784%	$158.8465	$158.85	$158.85	$158.80
7 purchase totals =	$617.55		$675.0373	$675.03	$675.05	$675.00