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	$67.66	5.666%	$71.4936	$71.49	$71.50	$71.50
Purchase #2	$202.33	10.162%	$222.8908	$222.89	$222.90	$222.90
Purchase #3	$73.69	9.456%	$80.6581	$80.66	$80.65	$80.70
Purchase #4	$101.40	5.356%	$106.831	$106.83	$106.85	$106.80
Purchase #5	$96.72	5.434%	$101.9758	$101.98	$102.00	$102.00
Purchase #6	$86.46	4.737%	$90.5556	$90.56	$90.55	$90.60
Purchase #7	$34.65	5.715%	$36.6302	$36.63	$36.65	$36.60
7 purchase totals =	$662.91		$711.0351	$711.04	$711.10	$711.10