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	$177.81	10.556%	$196.5796	$196.58	$196.60	$196.60
Purchase #2	$81.80	9.546%	$89.6086	$89.61	$89.60	$89.60
Purchase #3	$151.33	10.149%	$166.6885	$166.69	$166.70	$166.70
Purchase #4	$203.36	7.162%	$217.9246	$217.92	$217.90	$217.90
Purchase #5	$82.65	3.734%	$85.7362	$85.74	$85.75	$85.70
Purchase #6	$200.83	5.337%	$211.5483	$211.55	$211.55	$211.50
Purchase #7	$158.70	6.280%	$168.6664	$168.67	$168.65	$168.70
7 purchase totals =	$1,056.48		$1,136.7522	$1,136.76	$1,136.75	$1,136.70