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	$100.49	3.103%	$103.6082	$103.61	$103.60	$103.60
Purchase #2	$246.52	12.441%	$277.1896	$277.19	$277.20	$277.20
Purchase #3	$89.89	12.253%	$100.9042	$100.90	$100.90	$100.90
Purchase #4	$206.87	3.136%	$213.3574	$213.36	$213.35	$213.40
Purchase #5	$229.96	7.657%	$247.568	$247.57	$247.55	$247.60
Purchase #6	$52.79	12.735%	$59.5128	$59.51	$59.50	$59.50
Purchase #7	$147.64	11.704%	$164.9198	$164.92	$164.90	$164.90
7 purchase totals =	$1,074.16		$1,167.0600	$1,167.06	$1,167.00	$1,167.10