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	$174.93	3.803%	$181.5826	$181.58	$181.60	$181.60
Purchase #2	$242.40	3.358%	$250.5398	$250.54	$250.55	$250.50
Purchase #3	$218.82	12.617%	$246.4285	$246.43	$246.45	$246.40
Purchase #4	$197.55	12.570%	$222.382	$222.38	$222.40	$222.40
Purchase #5	$131.35	3.641%	$136.1325	$136.13	$136.15	$136.10
Purchase #6	$101.85	7.191%	$109.174	$109.17	$109.15	$109.20
Purchase #7	$174.54	7.489%	$187.6113	$187.61	$187.60	$187.60
7 purchase totals =	$1,241.44		$1,333.8507	$1,333.84	$1,333.90	$1,333.80