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	$134.73	4.171%	$140.3496	$140.35	$140.35	$140.30
Purchase #2	$199.41	13.379%	$226.0891	$226.09	$226.10	$226.10
Purchase #3	$224.75	7.793%	$242.2648	$242.26	$242.25	$242.30
Purchase #4	$236.32	5.652%	$249.6768	$249.68	$249.70	$249.70
Purchase #5	$39.37	3.243%	$40.6468	$40.65	$40.65	$40.60
Purchase #6	$45.36	10.553%	$50.1468	$50.15	$50.15	$50.10
Purchase #7	$101.57	10.856%	$112.5964	$112.60	$112.60	$112.60
7 purchase totals =	$981.51		$1,061.7703	$1,061.78	$1,061.80	$1,061.70