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	$71.42	5.365%	$75.2517	$75.25	$75.25	$75.30
Purchase #2	$166.96	4.724%	$174.8472	$174.85	$174.85	$174.80
Purchase #3	$147.72	5.522%	$155.8771	$155.88	$155.90	$155.90
Purchase #4	$91.76	9.476%	$100.4552	$100.46	$100.45	$100.50
Purchase #5	$62.76	13.277%	$71.0926	$71.09	$71.10	$71.10
Purchase #6	$233.62	3.732%	$242.3387	$242.34	$242.35	$242.30
Purchase #7	$239.91	11.104%	$266.5496	$266.55	$266.55	$266.50
7 purchase totals =	$1,014.15		$1,086.4121	$1,086.42	$1,086.45	$1,086.40