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	$160.33	3.364%	$165.7235	$165.72	$165.70	$165.70
Purchase #2	$133.38	7.633%	$143.5609	$143.56	$143.55	$143.60
Purchase #3	$93.43	3.426%	$96.6309	$96.63	$96.65	$96.60
Purchase #4	$245.61	8.820%	$267.2728	$267.27	$267.25	$267.30
Purchase #5	$245.79	11.510%	$274.0804	$274.08	$274.10	$274.10
Purchase #6	$71.52	9.685%	$78.4467	$78.45	$78.45	$78.40
Purchase #7	$148.90	10.317%	$164.262	$164.26	$164.25	$164.30
7 purchase totals =	$1,098.96		$1,189.9772	$1,189.97	$1,189.95	$1,190.00