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	$124.82	13.322%	$141.4485	$141.45	$141.45	$141.40
Purchase #2	$230.78	5.272%	$242.9467	$242.95	$242.95	$242.90
Purchase #3	$244.71	13.810%	$278.5045	$278.50	$278.50	$278.50
Purchase #4	$46.53	9.311%	$50.8624	$50.86	$50.85	$50.90
Purchase #5	$88.81	10.807%	$98.4077	$98.41	$98.40	$98.40
Purchase #6	$242.69	9.421%	$265.5538	$265.55	$265.55	$265.60
Purchase #7	$168.52	10.739%	$186.6174	$186.62	$186.60	$186.60
7 purchase totals =	$1,146.86		$1,264.3410	$1,264.34	$1,264.30	$1,264.30