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	$46.34	13.470%	$52.582	$52.58	$52.60	$52.60
Purchase #2	$169.89	13.165%	$192.256	$192.26	$192.25	$192.30
Purchase #3	$70.90	3.347%	$73.273	$73.27	$73.25	$73.30
Purchase #4	$230.41	5.325%	$242.6793	$242.68	$242.70	$242.70
Purchase #5	$72.59	7.535%	$78.0597	$78.06	$78.05	$78.10
Purchase #6	$231.89	5.307%	$244.1964	$244.20	$244.20	$244.20
Purchase #7	$117.33	9.341%	$128.2898	$128.29	$128.30	$128.30
7 purchase totals =	$939.35		$1,011.3362	$1,011.34	$1,011.35	$1,011.50