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	$83.33	13.545%	$94.617	$94.62	$94.60	$94.60
Purchase #2	$165.36	6.154%	$175.5363	$175.54	$175.55	$175.50
Purchase #3	$61.92	4.683%	$64.8197	$64.82	$64.80	$64.80
Purchase #4	$219.47	7.858%	$236.716	$236.72	$236.70	$236.70
Purchase #5	$95.52	7.269%	$102.4633	$102.46	$102.45	$102.50
Purchase #6	$179.56	11.800%	$200.7481	$200.75	$200.75	$200.70
Purchase #7	$95.95	9.839%	$105.3905	$105.39	$105.40	$105.40
7 purchase totals =	$901.11		$980.2909	$980.30	$980.25	$980.20