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	$176.81	4.874%	$185.4277	$185.43	$185.45	$185.40
Purchase #2	$209.53	8.264%	$226.8456	$226.85	$226.85	$226.80
Purchase #3	$223.29	7.533%	$240.1104	$240.11	$240.10	$240.10
Purchase #4	$10.65	11.710%	$11.8971	$11.90	$11.90	$11.90
Purchase #5	$227.29	10.285%	$250.6668	$250.67	$250.65	$250.70
Purchase #6	$116.58	4.547%	$121.8809	$121.88	$121.90	$121.90
Purchase #7	$92.33	7.718%	$99.456	$99.46	$99.45	$99.50
7 purchase totals =	$1,056.48		$1,136.2845	$1,136.30	$1,136.30	$1,136.30