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	$178.65	11.111%	$198.4998	$198.50	$198.50	$198.50
Purchase #2	$120.61	3.457%	$124.7795	$124.78	$124.80	$124.80
Purchase #3	$85.30	6.616%	$90.9434	$90.94	$90.95	$90.90
Purchase #4	$69.89	12.115%	$78.3572	$78.36	$78.35	$78.40
Purchase #5	$180.67	5.394%	$190.4153	$190.42	$190.40	$190.40
Purchase #6	$27.49	3.354%	$28.412	$28.41	$28.40	$28.40
Purchase #7	$134.31	12.783%	$151.4788	$151.48	$151.50	$151.50
7 purchase totals =	$796.92		$862.8860	$862.89	$862.90	$862.90