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	$99.55	5.807%	$105.3309	$105.33	$105.35	$105.30
Purchase #2	$246.96	6.397%	$262.758	$262.76	$262.75	$262.80
Purchase #3	$103.40	7.518%	$111.1736	$111.17	$111.15	$111.20
Purchase #4	$56.88	9.820%	$62.4656	$62.47	$62.45	$62.50
Purchase #5	$45.29	12.193%	$50.8122	$50.81	$50.80	$50.80
Purchase #6	$228.46	3.574%	$236.6252	$236.63	$236.65	$236.60
Purchase #7	$92.32	12.865%	$104.197	$104.20	$104.20	$104.20
7 purchase totals =	$872.86		$933.3625	$933.37	$933.35	$933.40