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	$237.55	4.260%	$247.6696	$247.67	$247.65	$247.70
Purchase #2	$118.89	3.758%	$123.3579	$123.36	$123.35	$123.40
Purchase #3	$82.96	6.264%	$88.1566	$88.16	$88.15	$88.20
Purchase #4	$86.36	11.138%	$95.9788	$95.98	$96.00	$96.00
Purchase #5	$55.97	5.593%	$59.1004	$59.10	$59.10	$59.10
Purchase #6	$79.41	7.759%	$85.5714	$85.57	$85.55	$85.60
Purchase #7	$193.52	11.473%	$215.7225	$215.72	$215.70	$215.70
7 purchase totals =	$854.66		$915.5572	$915.56	$915.50	$915.70