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	$179.61	4.425%	$187.5577	$187.56	$187.55	$187.60
Purchase #2	$109.74	4.280%	$114.4369	$114.44	$114.45	$114.40
Purchase #3	$104.35	6.477%	$111.1087	$111.11	$111.10	$111.10
Purchase #4	$99.85	7.310%	$107.149	$107.15	$107.15	$107.10
Purchase #5	$52.62	5.240%	$55.3773	$55.38	$55.40	$55.40
Purchase #6	$168.63	6.455%	$179.5151	$179.52	$179.50	$179.50
Purchase #7	$187.94	5.730%	$198.709	$198.71	$198.70	$198.70
7 purchase totals =	$902.74		$953.8537	$953.87	$953.85	$953.80