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	$98.58	12.688%	$111.0878	$111.09	$111.10	$111.10
Purchase #2	$35.68	5.600%	$37.6781	$37.68	$37.70	$37.70
Purchase #3	$218.49	12.186%	$245.1152	$245.12	$245.10	$245.10
Purchase #4	$27.83	12.498%	$31.3082	$31.31	$31.30	$31.30
Purchase #5	$58.62	7.111%	$62.7885	$62.79	$62.80	$62.80
Purchase #6	$141.55	5.176%	$148.8766	$148.88	$148.90	$148.90
Purchase #7	$161.76	9.127%	$176.5238	$176.52	$176.50	$176.50
7 purchase totals =	$742.51		$813.3782	$813.39	$813.40	$813.40