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	$182.37	5.161%	$191.7821	$191.78	$191.80	$191.80
Purchase #2	$149.54	11.442%	$166.6504	$166.65	$166.65	$166.70
Purchase #3	$5.81	6.279%	$6.1748	$6.17	$6.15	$6.20
Purchase #4	$234.43	11.838%	$262.1818	$262.18	$262.20	$262.20
Purchase #5	$98.91	12.839%	$111.6091	$111.61	$111.60	$111.60
Purchase #6	$97.97	6.817%	$104.6486	$104.65	$104.65	$104.60
Purchase #7	$90.75	8.127%	$98.1253	$98.13	$98.15	$98.10
7 purchase totals =	$859.78		$941.1721	$941.17	$941.20	$941.20