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	$160.46	8.836%	$174.6382	$174.64	$174.65	$174.60
Purchase #2	$227.40	12.349%	$255.4816	$255.48	$255.50	$255.50
Purchase #3	$97.44	5.563%	$102.8606	$102.86	$102.85	$102.90
Purchase #4	$173.94	3.253%	$179.5983	$179.60	$179.60	$179.60
Purchase #5	$37.26	3.768%	$38.664	$38.66	$38.65	$38.70
Purchase #6	$88.50	9.854%	$97.2208	$97.22	$97.20	$97.20
Purchase #7	$139.49	9.328%	$152.5016	$152.50	$152.50	$152.50
7 purchase totals =	$924.49		$1,000.9651	$1,000.96	$1,000.95	$1,001.00