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	$204.47	11.427%	$227.8348	$227.83	$227.85	$227.80
Purchase #2	$62.43	8.497%	$67.7347	$67.73	$67.75	$67.70
Purchase #3	$123.81	7.688%	$133.3285	$133.33	$133.35	$133.30
Purchase #4	$226.56	6.102%	$240.3847	$240.38	$240.40	$240.40
Purchase #5	$201.56	12.514%	$226.7832	$226.78	$226.80	$226.80
Purchase #6	$83.78	6.693%	$89.3874	$89.39	$89.40	$89.40
Purchase #7	$245.77	10.258%	$270.9811	$270.98	$271.00	$271.00
7 purchase totals =	$1,148.38		$1,256.4344	$1,256.42	$1,256.55	$1,256.40