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	$142.90	13.420%	$162.0772	$162.08	$162.10	$162.10
Purchase #2	$225.50	13.258%	$255.3968	$255.40	$255.40	$255.40
Purchase #3	$179.25	9.482%	$196.2465	$196.25	$196.25	$196.20
Purchase #4	$114.73	12.317%	$128.8613	$128.86	$128.85	$128.90
Purchase #5	$174.77	9.194%	$190.8384	$190.84	$190.85	$190.80
Purchase #6	$46.65	7.321%	$50.0652	$50.07	$50.05	$50.10
Purchase #7	$150.96	3.276%	$155.9054	$155.91	$155.90	$155.90
7 purchase totals =	$1,034.76		$1,139.3908	$1,139.41	$1,139.40	$1,139.40