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	$223.68	6.633%	$238.5167	$238.52	$238.50	$238.50
Purchase #2	$233.87	10.521%	$258.4755	$258.48	$258.50	$258.50
Purchase #3	$217.53	12.831%	$245.4413	$245.44	$245.45	$245.40
Purchase #4	$88.95	7.221%	$95.3731	$95.37	$95.35	$95.40
Purchase #5	$140.86	12.413%	$158.345	$158.35	$158.35	$158.30
Purchase #6	$59.53	13.590%	$67.6201	$67.62	$67.60	$67.60
Purchase #7	$11.73	12.511%	$13.1975	$13.20	$13.20	$13.20
7 purchase totals =	$976.15		$1,076.9692	$1,076.98	$1,076.95	$1,076.90