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	$116.28	3.631%	$120.5021	$120.50	$120.50	$120.50
Purchase #2	$185.59	5.691%	$196.1519	$196.15	$196.15	$196.20
Purchase #3	$71.78	11.533%	$80.0584	$80.06	$80.05	$80.10
Purchase #4	$232.75	9.829%	$255.627	$255.63	$255.65	$255.60
Purchase #5	$249.27	10.263%	$274.8526	$274.85	$274.85	$274.90
Purchase #6	$124.80	5.107%	$131.1735	$131.17	$131.15	$131.20
Purchase #7	$133.78	6.824%	$142.9091	$142.91	$142.90	$142.90
7 purchase totals =	$1,114.25		$1,201.2746	$1,201.27	$1,201.25	$1,201.40