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	$227.29	4.340%	$237.1544	$237.15	$237.15	$237.20
Purchase #2	$79.43	4.304%	$82.8487	$82.85	$82.85	$82.80
Purchase #3	$93.33	11.682%	$104.2328	$104.23	$104.25	$104.20
Purchase #4	$164.42	9.274%	$179.6683	$179.67	$179.65	$179.70
Purchase #5	$200.98	13.389%	$227.8892	$227.89	$227.90	$227.90
Purchase #6	$135.49	7.134%	$145.1559	$145.16	$145.15	$145.20
Purchase #7	$38.71	5.606%	$40.8801	$40.88	$40.90	$40.90
7 purchase totals =	$939.65		$1,017.8294	$1,017.83	$1,017.85	$1,017.90