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	$95.61	10.305%	$105.4626	$105.46	$105.45	$105.50
Purchase #2	$164.44	4.337%	$171.5718	$171.57	$171.55	$171.60
Purchase #3	$125.89	12.611%	$141.766	$141.77	$141.75	$141.80
Purchase #4	$124.65	13.709%	$141.7383	$141.74	$141.75	$141.70
Purchase #5	$98.25	6.176%	$104.3179	$104.32	$104.30	$104.30
Purchase #6	$229.54	3.432%	$237.4178	$237.42	$237.40	$237.40
Purchase #7	$127.67	10.460%	$141.0243	$141.02	$141.00	$141.00
7 purchase totals =	$966.05		$1,043.2987	$1,043.30	$1,043.20	$1,043.30