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	$48.85	10.248%	$53.8561	$53.86	$53.85	$53.90
Purchase #2	$154.40	8.757%	$167.9208	$167.92	$167.90	$167.90
Purchase #3	$88.92	7.380%	$95.4823	$95.48	$95.50	$95.50
Purchase #4	$239.76	12.161%	$268.9172	$268.92	$268.90	$268.90
Purchase #5	$185.38	9.823%	$203.5899	$203.59	$203.60	$203.60
Purchase #6	$154.42	6.692%	$164.7538	$164.75	$164.75	$164.80
Purchase #7	$143.78	7.685%	$154.8295	$154.83	$154.85	$154.80
7 purchase totals =	$1,015.51		$1,109.3496	$1,109.35	$1,109.35	$1,109.40