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	$67.33	13.767%	$76.5993	$76.60	$76.60	$76.60
Purchase #2	$173.60	3.300%	$179.3288	$179.33	$179.35	$179.30
Purchase #3	$121.96	9.293%	$133.2937	$133.29	$133.30	$133.30
Purchase #4	$224.59	3.479%	$232.4035	$232.40	$232.40	$232.40
Purchase #5	$178.78	9.685%	$196.0948	$196.09	$196.10	$196.10
Purchase #6	$241.96	5.173%	$254.4766	$254.48	$254.50	$254.50
Purchase #7	$131.60	9.780%	$144.4705	$144.47	$144.45	$144.50
7 purchase totals =	$1,139.82		$1,216.6672	$1,216.66	$1,216.70	$1,216.70