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	$57.53	7.626%	$61.9172	$61.92	$61.90	$61.90
Purchase #2	$236.75	11.228%	$263.3323	$263.33	$263.35	$263.30
Purchase #3	$43.76	5.721%	$46.2635	$46.26	$46.25	$46.30
Purchase #4	$234.89	9.662%	$257.5851	$257.59	$257.60	$257.60
Purchase #5	$167.67	11.680%	$187.2539	$187.25	$187.25	$187.30
Purchase #6	$76.67	4.631%	$80.2206	$80.22	$80.20	$80.20
Purchase #7	$168.57	6.545%	$179.6029	$179.60	$179.60	$179.60
7 purchase totals =	$985.84		$1,076.1755	$1,076.17	$1,076.15	$1,076.20