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	$130.72	9.480%	$143.1123	$143.11	$143.10	$143.10
Purchase #2	$214.40	9.296%	$234.3306	$234.33	$234.35	$234.30
Purchase #3	$154.54	4.560%	$161.587	$161.59	$161.60	$161.60
Purchase #4	$242.62	12.716%	$273.4716	$273.47	$273.45	$273.50
Purchase #5	$80.91	12.546%	$91.061	$91.06	$91.05	$91.10
Purchase #6	$39.37	10.848%	$43.6409	$43.64	$43.65	$43.60
Purchase #7	$133.79	10.709%	$148.1176	$148.12	$148.10	$148.10
7 purchase totals =	$996.35		$1,095.3210	$1,095.32	$1,095.30	$1,095.30