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	$61.95	5.230%	$65.19	$65.19	$65.20	$65.20
Purchase #2	$63.63	3.529%	$65.8755	$65.88	$65.90	$65.90
Purchase #3	$84.44	6.303%	$89.7623	$89.76	$89.75	$89.80
Purchase #4	$95.50	4.197%	$99.5081	$99.51	$99.50	$99.50
Purchase #5	$101.76	3.132%	$104.9471	$104.95	$104.95	$104.90
Purchase #6	$150.60	8.702%	$163.7052	$163.71	$163.70	$163.70
Purchase #7	$81.56	12.144%	$91.4646	$91.46	$91.45	$91.50
7 purchase totals =	$639.44		$680.4528	$680.46	$680.45	$680.50