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	$136.65	13.136%	$154.6003	$154.60	$154.60	$154.60
Purchase #2	$30.63	9.716%	$33.606	$33.61	$33.60	$33.60
Purchase #3	$244.96	9.152%	$267.3787	$267.38	$267.40	$267.40
Purchase #4	$186.92	13.423%	$212.0103	$212.01	$212.00	$212.00
Purchase #5	$89.45	8.352%	$96.9209	$96.92	$96.90	$96.90
Purchase #6	$143.45	6.457%	$152.7126	$152.71	$152.70	$152.70
Purchase #7	$93.78	9.441%	$102.6338	$102.63	$102.65	$102.60
7 purchase totals =	$925.84		$1,019.8626	$1,019.86	$1,019.85	$1,019.80