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	$184.98	6.403%	$196.8243	$196.82	$196.80	$196.80
Purchase #2	$84.40	8.123%	$91.2558	$91.26	$91.25	$91.30
Purchase #3	$241.82	10.175%	$266.4252	$266.43	$266.45	$266.40
Purchase #4	$57.36	3.848%	$59.5672	$59.57	$59.55	$59.60
Purchase #5	$248.65	8.604%	$270.0438	$270.04	$270.05	$270.00
Purchase #6	$176.39	4.281%	$183.9413	$183.94	$183.95	$183.90
Purchase #7	$129.54	10.279%	$142.8554	$142.86	$142.85	$142.90
7 purchase totals =	$1,123.14		$1,210.9130	$1,210.92	$1,210.90	$1,210.90