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	$42.35	7.354%	$45.4644	$45.46	$45.45	$45.50
Purchase #2	$48.36	7.253%	$51.8676	$51.87	$51.85	$51.90
Purchase #3	$36.83	5.533%	$38.8678	$38.87	$38.85	$38.90
Purchase #4	$74.31	11.195%	$82.629	$82.63	$82.65	$82.60
Purchase #5	$108.70	4.132%	$113.1915	$113.19	$113.20	$113.20
Purchase #6	$214.85	3.433%	$222.2258	$222.23	$222.25	$222.20
Purchase #7	$112.93	3.343%	$116.7052	$116.71	$116.70	$116.70
7 purchase totals =	$638.33		$670.9513	$670.96	$670.95	$671.00