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	$174.99	3.557%	$181.2144	$181.21	$181.20	$181.20
Purchase #2	$225.35	13.373%	$255.4861	$255.49	$255.50	$255.50
Purchase #3	$57.83	3.300%	$59.7384	$59.74	$59.75	$59.70
Purchase #4	$235.47	4.263%	$245.5081	$245.51	$245.50	$245.50
Purchase #5	$135.43	11.168%	$150.5548	$150.55	$150.55	$150.60
Purchase #6	$178.58	4.337%	$186.325	$186.33	$186.35	$186.30
Purchase #7	$224.28	7.619%	$241.3679	$241.37	$241.35	$241.40
7 purchase totals =	$1,231.93		$1,320.1947	$1,320.20	$1,320.20	$1,320.20