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	$204.96	13.133%	$231.8774	$231.88	$231.90	$231.90
Purchase #2	$28.40	4.732%	$29.7439	$29.74	$29.75	$29.70
Purchase #3	$157.73	6.836%	$168.5124	$168.51	$168.50	$168.50
Purchase #4	$216.90	11.616%	$242.0951	$242.10	$242.10	$242.10
Purchase #5	$149.80	8.707%	$162.8431	$162.84	$162.85	$162.80
Purchase #6	$156.50	8.322%	$169.5239	$169.52	$169.50	$169.50
Purchase #7	$29.56	6.705%	$31.542	$31.54	$31.55	$31.50
7 purchase totals =	$943.85		$1,036.1378	$1,036.13	$1,036.15	$1,036.00