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	$81.56	13.791%	$92.8079	$92.81	$92.80	$92.80
Purchase #2	$73.78	3.122%	$76.0834	$76.08	$76.10	$76.10
Purchase #3	$250.75	5.337%	$264.1325	$264.13	$264.15	$264.10
Purchase #4	$142.78	10.533%	$157.819	$157.82	$157.80	$157.80
Purchase #5	$162.60	11.655%	$181.551	$181.55	$181.55	$181.60
Purchase #6	$40.46	3.709%	$41.9607	$41.96	$41.95	$42.00
Purchase #7	$149.89	11.555%	$167.2098	$167.21	$167.20	$167.20
7 purchase totals =	$901.82		$981.5643	$981.56	$981.55	$981.60