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	$167.47	10.799%	$185.5551	$185.56	$185.55	$185.60
Purchase #2	$131.81	6.512%	$140.3935	$140.39	$140.40	$140.40
Purchase #3	$128.69	9.536%	$140.9619	$140.96	$140.95	$141.00
Purchase #4	$83.42	6.512%	$88.8523	$88.85	$88.85	$88.90
Purchase #5	$92.29	13.414%	$104.6698	$104.67	$104.65	$104.70
Purchase #6	$103.33	7.502%	$111.0818	$111.08	$111.10	$111.10
Purchase #7	$156.82	9.808%	$172.2009	$172.20	$172.20	$172.20
7 purchase totals =	$863.83		$943.7153	$943.71	$943.70	$943.90