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	$84.29	7.588%	$90.6859	$90.69	$90.70	$90.70
Purchase #2	$70.31	11.134%	$78.1383	$78.14	$78.15	$78.10
Purchase #3	$85.45	5.391%	$90.0566	$90.06	$90.05	$90.10
Purchase #4	$136.46	5.721%	$144.2669	$144.27	$144.25	$144.30
Purchase #5	$194.77	3.486%	$201.5597	$201.56	$201.55	$201.60
Purchase #6	$200.41	5.418%	$211.2682	$211.27	$211.25	$211.30
Purchase #7	$217.33	3.325%	$224.5562	$224.56	$224.55	$224.60
7 purchase totals =	$989.02		$1,040.5318	$1,040.55	$1,040.50	$1,040.70