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	$142.97	6.619%	$152.4332	$152.43	$152.45	$152.40
Purchase #2	$34.76	10.414%	$38.3799	$38.38	$38.40	$38.40
Purchase #3	$229.52	5.704%	$242.6118	$242.61	$242.60	$242.60
Purchase #4	$105.69	3.192%	$109.0636	$109.06	$109.05	$109.10
Purchase #5	$187.46	5.318%	$197.4291	$197.43	$197.45	$197.40
Purchase #6	$25.82	4.607%	$27.0095	$27.01	$27.00	$27.00
Purchase #7	$153.50	11.806%	$171.6222	$171.62	$171.60	$171.60
7 purchase totals =	$879.72		$938.5493	$938.54	$938.55	$938.50