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	$148.87	7.208%	$159.6005	$159.60	$159.60	$159.60
Purchase #2	$21.87	7.207%	$23.4462	$23.45	$23.45	$23.40
Purchase #3	$82.71	9.489%	$90.5584	$90.56	$90.55	$90.60
Purchase #4	$240.61	7.360%	$258.3189	$258.32	$258.30	$258.30
Purchase #5	$200.56	5.839%	$212.2707	$212.27	$212.25	$212.30
Purchase #6	$164.88	9.675%	$180.8321	$180.83	$180.85	$180.80
Purchase #7	$129.84	13.588%	$147.4827	$147.48	$147.50	$147.50
7 purchase totals =	$989.34		$1,072.5095	$1,072.51	$1,072.50	$1,072.50