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	$89.49	6.297%	$95.1252	$95.13	$95.15	$95.10
Purchase #2	$37.71	8.676%	$40.9817	$40.98	$41.00	$41.00
Purchase #3	$124.51	3.111%	$128.3835	$128.38	$128.40	$128.40
Purchase #4	$244.32	4.479%	$255.2631	$255.26	$255.25	$255.30
Purchase #5	$104.82	8.318%	$113.5389	$113.54	$113.55	$113.50
Purchase #6	$105.61	7.724%	$113.7673	$113.77	$113.75	$113.80
Purchase #7	$110.96	7.253%	$119.0079	$119.01	$119.00	$119.00
7 purchase totals =	$817.42		$866.0676	$866.07	$866.10	$866.10