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	$135.28	9.243%	$147.7839	$147.78	$147.80	$147.80
Purchase #2	$54.81	13.844%	$62.3979	$62.40	$62.40	$62.40
Purchase #3	$157.44	4.609%	$164.6964	$164.70	$164.70	$164.70
Purchase #4	$89.51	5.773%	$94.6774	$94.68	$94.70	$94.70
Purchase #5	$94.39	3.356%	$97.5577	$97.56	$97.55	$97.60
Purchase #6	$249.89	8.197%	$270.3735	$270.37	$270.35	$270.40
Purchase #7	$157.83	4.479%	$164.8992	$164.90	$164.90	$164.90
7 purchase totals =	$939.15		$1,002.3860	$1,002.39	$1,002.40	$1,002.50