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	$220.95	3.477%	$228.6324	$228.63	$228.65	$228.60
Purchase #2	$216.32	7.768%	$233.1237	$233.12	$233.10	$233.10
Purchase #3	$178.31	10.319%	$196.7098	$196.71	$196.70	$196.70
Purchase #4	$115.65	7.561%	$124.3943	$124.39	$124.40	$124.40
Purchase #5	$171.44	9.406%	$187.5656	$187.57	$187.55	$187.60
Purchase #6	$64.56	9.767%	$70.8656	$70.87	$70.85	$70.90
Purchase #7	$119.64	9.155%	$130.593	$130.59	$130.60	$130.60
7 purchase totals =	$1,086.87		$1,171.8844	$1,171.88	$1,171.85	$1,171.90