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	$111.96	3.153%	$115.4901	$115.49	$115.50	$115.50
Purchase #2	$76.60	4.140%	$79.7712	$79.77	$79.75	$79.80
Purchase #3	$161.37	11.233%	$179.4967	$179.50	$179.50	$179.50
Purchase #4	$221.89	10.269%	$244.6759	$244.68	$244.70	$244.70
Purchase #5	$212.77	6.134%	$225.8213	$225.82	$225.80	$225.80
Purchase #6	$40.25	5.767%	$42.5712	$42.57	$42.55	$42.60
Purchase #7	$171.65	12.781%	$193.5886	$193.59	$193.60	$193.60
7 purchase totals =	$996.49		$1,081.4150	$1,081.42	$1,081.40	$1,081.50