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	$96.42	12.259%	$108.2401	$108.24	$108.25	$108.20
Purchase #2	$62.86	10.472%	$69.4427	$69.44	$69.45	$69.40
Purchase #3	$158.47	13.788%	$180.3198	$180.32	$180.30	$180.30
Purchase #4	$131.46	12.359%	$147.7071	$147.71	$147.70	$147.70
Purchase #5	$182.75	5.653%	$193.0809	$193.08	$193.10	$193.10
Purchase #6	$187.83	5.661%	$198.4631	$198.46	$198.45	$198.50
Purchase #7	$173.45	13.329%	$196.5692	$196.57	$196.55	$196.60
7 purchase totals =	$993.24		$1,093.8229	$1,093.82	$1,093.80	$1,093.80