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	$57.86	6.711%	$61.743	$61.74	$61.75	$61.70
Purchase #2	$29.50	7.370%	$31.6742	$31.67	$31.65	$31.70
Purchase #3	$100.33	10.488%	$110.8526	$110.85	$110.85	$110.90
Purchase #4	$182.25	7.751%	$196.3762	$196.38	$196.40	$196.40
Purchase #5	$140.89	13.443%	$159.8298	$159.83	$159.85	$159.80
Purchase #6	$114.96	3.157%	$118.5893	$118.59	$118.60	$118.60
Purchase #7	$198.71	12.824%	$224.1926	$224.19	$224.20	$224.20
7 purchase totals =	$824.50		$903.2577	$903.25	$903.30	$903.30