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	$209.90	10.440%	$231.8136	$231.81	$231.80	$231.80
Purchase #2	$199.36	12.210%	$223.7019	$223.70	$223.70	$223.70
Purchase #3	$174.38	6.407%	$185.5525	$185.55	$185.55	$185.60
Purchase #4	$89.27	12.573%	$100.4939	$100.49	$100.50	$100.50
Purchase #5	$12.76	8.799%	$13.8828	$13.88	$13.90	$13.90
Purchase #6	$208.70	7.672%	$224.7115	$224.71	$224.70	$224.70
Purchase #7	$114.25	3.782%	$118.5709	$118.57	$118.55	$118.60
7 purchase totals =	$1,008.62		$1,098.7271	$1,098.71	$1,098.70	$1,098.80