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	$161.39	3.419%	$166.9079	$166.91	$166.90	$166.90
Purchase #2	$243.77	5.655%	$257.5552	$257.56	$257.55	$257.60
Purchase #3	$77.83	5.688%	$82.257	$82.26	$82.25	$82.30
Purchase #4	$126.56	3.565%	$131.0719	$131.07	$131.05	$131.10
Purchase #5	$130.51	10.599%	$144.3428	$144.34	$144.35	$144.30
Purchase #6	$236.73	9.781%	$259.8846	$259.88	$259.90	$259.90
Purchase #7	$163.65	3.527%	$169.4219	$169.42	$169.40	$169.40
7 purchase totals =	$1,140.44		$1,211.4413	$1,211.44	$1,211.40	$1,211.50