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	$128.63	11.539%	$143.4726	$143.47	$143.45	$143.50
Purchase #2	$238.25	13.144%	$269.5656	$269.57	$269.55	$269.60
Purchase #3	$68.51	4.371%	$71.5046	$71.50	$71.50	$71.50
Purchase #4	$33.36	10.425%	$36.8378	$36.84	$36.85	$36.80
Purchase #5	$131.42	12.290%	$147.5715	$147.57	$147.55	$147.60
Purchase #6	$187.61	4.591%	$196.2232	$196.22	$196.20	$196.20
Purchase #7	$106.81	12.759%	$120.4379	$120.44	$120.45	$120.40
7 purchase totals =	$894.59		$985.6132	$985.61	$985.55	$985.60