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	$225.53	3.596%	$233.6401	$233.64	$233.65	$233.60
Purchase #2	$54.49	8.839%	$59.3064	$59.31	$59.30	$59.30
Purchase #3	$161.62	10.110%	$177.9598	$177.96	$177.95	$178.00
Purchase #4	$217.72	3.514%	$225.3707	$225.37	$225.35	$225.40
Purchase #5	$96.77	9.291%	$105.7609	$105.76	$105.75	$105.80
Purchase #6	$82.66	9.650%	$90.6367	$90.64	$90.65	$90.60
Purchase #7	$144.90	3.299%	$149.6803	$149.68	$149.70	$149.70
7 purchase totals =	$983.69		$1,042.3549	$1,042.36	$1,042.35	$1,042.40