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	$167.37	8.478%	$181.5596	$181.56	$181.55	$181.60
Purchase #2	$169.67	5.773%	$179.465	$179.47	$179.45	$179.50
Purchase #3	$126.94	12.260%	$142.5028	$142.50	$142.50	$142.50
Purchase #4	$147.75	13.711%	$168.008	$168.01	$168.00	$168.00
Purchase #5	$221.71	7.134%	$237.5268	$237.53	$237.55	$237.50
Purchase #6	$125.25	4.671%	$131.1004	$131.10	$131.10	$131.10
Purchase #7	$152.71	8.632%	$165.8919	$165.89	$165.90	$165.90
7 purchase totals =	$1,111.40		$1,206.0545	$1,206.06	$1,206.05	$1,206.10