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	$67.44	12.644%	$75.9671	$75.97	$75.95	$76.00
Purchase #2	$230.93	13.262%	$261.5559	$261.56	$261.55	$261.60
Purchase #3	$225.80	4.685%	$236.3787	$236.38	$236.40	$236.40
Purchase #4	$33.35	12.648%	$37.5681	$37.57	$37.55	$37.60
Purchase #5	$40.81	11.184%	$45.3742	$45.37	$45.35	$45.40
Purchase #6	$152.38	7.678%	$164.0797	$164.08	$164.10	$164.10
Purchase #7	$173.96	4.557%	$181.8874	$181.89	$181.90	$181.90
7 purchase totals =	$924.67		$1,002.8111	$1,002.82	$1,002.80	$1,003.00