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	$203.48	9.533%	$222.8777	$222.88	$222.90	$222.90
Purchase #2	$51.78	5.195%	$54.47	$54.47	$54.45	$54.50
Purchase #3	$206.76	11.800%	$231.1577	$231.16	$231.15	$231.20
Purchase #4	$164.52	8.426%	$178.3825	$178.38	$178.40	$178.40
Purchase #5	$61.43	9.790%	$67.444	$67.44	$67.45	$67.40
Purchase #6	$102.96	3.742%	$106.8128	$106.81	$106.80	$106.80
Purchase #7	$99.58	6.133%	$105.6872	$105.69	$105.70	$105.70
7 purchase totals =	$890.51		$966.8319	$966.83	$966.85	$966.90