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	$130.73	8.446%	$141.7715	$141.77	$141.75	$141.80
Purchase #2	$189.42	3.829%	$196.6729	$196.67	$196.65	$196.70
Purchase #3	$224.90	3.488%	$232.7445	$232.74	$232.75	$232.70
Purchase #4	$89.92	12.170%	$100.8633	$100.86	$100.85	$100.90
Purchase #5	$194.61	11.321%	$216.6418	$216.64	$216.65	$216.60
Purchase #6	$223.65	7.732%	$240.9426	$240.94	$240.95	$240.90
Purchase #7	$6.66	3.553%	$6.8966	$6.90	$6.90	$6.90
7 purchase totals =	$1,059.89		$1,136.5332	$1,136.52	$1,136.50	$1,136.50