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	$117.78	5.280%	$123.9988	$124.00	$124.00	$124.00
Purchase #2	$203.99	12.290%	$229.0604	$229.06	$229.05	$229.10
Purchase #3	$78.85	4.284%	$82.2279	$82.23	$82.25	$82.20
Purchase #4	$142.29	3.518%	$147.2958	$147.30	$147.30	$147.30
Purchase #5	$161.72	3.522%	$167.4158	$167.42	$167.40	$167.40
Purchase #6	$181.76	4.854%	$190.5826	$190.58	$190.60	$190.60
Purchase #7	$38.96	11.347%	$43.3808	$43.38	$43.40	$43.40
7 purchase totals =	$925.35		$983.9621	$983.97	$984.00	$984.00