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	$33.64	3.146%	$34.6983	$34.70	$34.70	$34.70
Purchase #2	$233.55	9.430%	$255.5738	$255.57	$255.55	$255.60
Purchase #3	$93.90	6.188%	$99.7105	$99.71	$99.70	$99.70
Purchase #4	$168.90	9.478%	$184.9083	$184.91	$184.90	$184.90
Purchase #5	$93.75	9.768%	$102.9075	$102.91	$102.90	$102.90
Purchase #6	$80.87	10.849%	$89.6436	$89.64	$89.65	$89.60
Purchase #7	$249.25	9.302%	$272.4352	$272.44	$272.45	$272.40
7 purchase totals =	$953.86		$1,039.8772	$1,039.88	$1,039.85	$1,039.80