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	$46.47	13.558%	$52.7704	$52.77	$52.75	$52.80
Purchase #2	$182.57	7.746%	$196.7119	$196.71	$196.70	$196.70
Purchase #3	$238.30	4.242%	$248.4087	$248.41	$248.40	$248.40
Purchase #4	$26.72	6.171%	$28.3689	$28.37	$28.35	$28.40
Purchase #5	$75.51	13.748%	$85.8911	$85.89	$85.90	$85.90
Purchase #6	$51.25	4.438%	$53.5245	$53.52	$53.50	$53.50
Purchase #7	$96.90	12.119%	$108.6433	$108.64	$108.65	$108.60
7 purchase totals =	$717.72		$774.3188	$774.31	$774.25	$774.30