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	$196.35	10.793%	$217.5421	$217.54	$217.55	$217.50
Purchase #2	$61.72	11.298%	$68.6931	$68.69	$68.70	$68.70
Purchase #3	$57.82	7.488%	$62.1496	$62.15	$62.15	$62.10
Purchase #4	$225.48	6.705%	$240.5984	$240.60	$240.60	$240.60
Purchase #5	$135.82	11.186%	$151.0128	$151.01	$151.00	$151.00
Purchase #6	$112.29	10.322%	$123.8806	$123.88	$123.90	$123.90
Purchase #7	$64.79	9.538%	$70.9697	$70.97	$70.95	$71.00
7 purchase totals =	$854.27		$934.8463	$934.84	$934.85	$934.80