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	$214.97	10.696%	$237.9632	$237.96	$237.95	$238.00
Purchase #2	$56.56	11.197%	$62.893	$62.89	$62.90	$62.90
Purchase #3	$114.26	4.222%	$119.0841	$119.08	$119.10	$119.10
Purchase #4	$83.66	10.599%	$92.5271	$92.53	$92.55	$92.50
Purchase #5	$152.70	11.356%	$170.0406	$170.04	$170.05	$170.00
Purchase #6	$72.67	13.585%	$82.5422	$82.54	$82.55	$82.50
Purchase #7	$91.96	11.229%	$102.2862	$102.29	$102.30	$102.30
7 purchase totals =	$786.78		$867.3364	$867.33	$867.40	$867.30