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	$72.71	13.871%	$82.7956	$82.80	$82.80	$82.80
Purchase #2	$225.62	6.458%	$240.1905	$240.19	$240.20	$240.20
Purchase #3	$156.25	3.765%	$162.1328	$162.13	$162.15	$162.10
Purchase #4	$65.86	8.536%	$71.4818	$71.48	$71.50	$71.50
Purchase #5	$101.45	6.750%	$108.2979	$108.30	$108.30	$108.30
Purchase #6	$242.81	3.614%	$251.5852	$251.59	$251.60	$251.60
Purchase #7	$127.59	13.105%	$144.3107	$144.31	$144.30	$144.30
7 purchase totals =	$992.29		$1,060.7945	$1,060.80	$1,060.85	$1,060.80