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	$193.37	5.374%	$203.7617	$203.76	$203.75	$203.80
Purchase #2	$178.50	12.387%	$200.6108	$200.61	$200.60	$200.60
Purchase #3	$100.75	11.490%	$112.3262	$112.33	$112.35	$112.30
Purchase #4	$43.45	10.154%	$47.8619	$47.86	$47.85	$47.90
Purchase #5	$156.97	3.527%	$162.5063	$162.51	$162.50	$162.50
Purchase #6	$150.81	9.218%	$164.7117	$164.71	$164.70	$164.70
Purchase #7	$118.98	7.827%	$128.2926	$128.29	$128.30	$128.30
7 purchase totals =	$942.83		$1,020.0712	$1,020.07	$1,020.05	$1,020.10