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	$154.43	7.590%	$166.1512	$166.15	$166.15	$166.20
Purchase #2	$166.48	3.812%	$172.8262	$172.83	$172.85	$172.80
Purchase #3	$164.51	3.604%	$170.4389	$170.44	$170.45	$170.40
Purchase #4	$40.61	6.612%	$43.2951	$43.30	$43.30	$43.30
Purchase #5	$77.41	13.798%	$88.091	$88.09	$88.10	$88.10
Purchase #6	$119.62	6.211%	$127.0496	$127.05	$127.05	$127.00
Purchase #7	$227.74	6.641%	$242.8642	$242.86	$242.85	$242.90
7 purchase totals =	$950.80		$1,010.7162	$1,010.72	$1,010.75	$1,010.70