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	$48.95	11.874%	$54.7623	$54.76	$54.75	$54.80
Purchase #2	$27.94	12.598%	$31.4599	$31.46	$31.45	$31.50
Purchase #3	$51.83	4.619%	$54.224	$54.22	$54.20	$54.20
Purchase #4	$219.38	12.481%	$246.7608	$246.76	$246.75	$246.80
Purchase #5	$96.61	7.499%	$103.8548	$103.85	$103.85	$103.90
Purchase #6	$249.54	3.843%	$259.1298	$259.13	$259.15	$259.10
Purchase #7	$211.30	12.302%	$237.2941	$237.29	$237.30	$237.30
7 purchase totals =	$905.55		$987.4857	$987.47	$987.45	$987.60