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	$212.37	9.526%	$232.6004	$232.60	$232.60	$232.60
Purchase #2	$137.89	3.507%	$142.7258	$142.73	$142.75	$142.70
Purchase #3	$214.33	12.225%	$240.5318	$240.53	$240.55	$240.50
Purchase #4	$158.81	7.767%	$171.1448	$171.14	$171.15	$171.10
Purchase #5	$170.70	10.118%	$187.9714	$187.97	$187.95	$188.00
Purchase #6	$245.30	4.179%	$255.5511	$255.55	$255.55	$255.60
Purchase #7	$112.82	12.804%	$127.2655	$127.27	$127.25	$127.30
7 purchase totals =	$1,252.22		$1,357.7908	$1,357.79	$1,357.80	$1,357.80