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	$130.83	8.359%	$141.7661	$141.77	$141.75	$141.80
Purchase #2	$82.52	4.824%	$86.5008	$86.50	$86.50	$86.50
Purchase #3	$102.41	5.365%	$107.9043	$107.90	$107.90	$107.90
Purchase #4	$234.78	11.813%	$262.5146	$262.51	$262.50	$262.50
Purchase #5	$204.79	3.660%	$212.2853	$212.29	$212.30	$212.30
Purchase #6	$152.75	11.793%	$170.7638	$170.76	$170.75	$170.80
Purchase #7	$52.95	12.581%	$59.6116	$59.61	$59.60	$59.60
7 purchase totals =	$961.03		$1,041.3465	$1,041.34	$1,041.30	$1,041.40