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	$193.34	8.416%	$209.6115	$209.61	$209.60	$209.60
Purchase #2	$142.80	11.211%	$158.8093	$158.81	$158.80	$158.80
Purchase #3	$191.51	3.462%	$198.1401	$198.14	$198.15	$198.10
Purchase #4	$40.37	8.581%	$43.8341	$43.83	$43.85	$43.80
Purchase #5	$152.83	4.222%	$159.2825	$159.28	$159.30	$159.30
Purchase #6	$149.79	4.556%	$156.6144	$156.61	$156.60	$156.60
Purchase #7	$104.97	8.612%	$114.01	$114.01	$114.00	$114.00
7 purchase totals =	$975.61		$1,040.3019	$1,040.29	$1,040.30	$1,040.20