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	$194.90	13.500%	$221.2115	$221.21	$221.20	$221.20
Purchase #2	$76.93	7.241%	$82.5005	$82.50	$82.50	$82.50
Purchase #3	$82.98	8.458%	$89.9984	$90.00	$90.00	$90.00
Purchase #4	$106.46	6.792%	$113.6908	$113.69	$113.70	$113.70
Purchase #5	$194.85	8.338%	$211.0966	$211.10	$211.10	$211.10
Purchase #6	$217.35	6.617%	$231.732	$231.73	$231.75	$231.70
Purchase #7	$58.48	5.716%	$61.8227	$61.82	$61.80	$61.80
7 purchase totals =	$931.95		$1,012.0525	$1,012.05	$1,012.05	$1,012.00