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	$160.46	8.671%	$174.3735	$174.37	$174.35	$174.40
Purchase #2	$185.36	13.606%	$210.5801	$210.58	$210.60	$210.60
Purchase #3	$247.46	3.537%	$256.2127	$256.21	$256.20	$256.20
Purchase #4	$38.82	8.294%	$42.0397	$42.04	$42.05	$42.00
Purchase #5	$241.86	5.383%	$254.8793	$254.88	$254.90	$254.90
Purchase #6	$164.27	4.297%	$171.3287	$171.33	$171.35	$171.30
Purchase #7	$215.38	12.849%	$243.0542	$243.05	$243.05	$243.10
7 purchase totals =	$1,253.61		$1,352.4682	$1,352.46	$1,352.50	$1,352.50