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	$170.59	7.564%	$183.4934	$183.49	$183.50	$183.50
Purchase #2	$75.30	4.221%	$78.4784	$78.48	$78.50	$78.50
Purchase #3	$227.83	7.297%	$244.4548	$244.45	$244.45	$244.50
Purchase #4	$191.48	3.432%	$198.0516	$198.05	$198.05	$198.10
Purchase #5	$222.81	9.536%	$244.0572	$244.06	$244.05	$244.10
Purchase #6	$129.57	11.575%	$144.5677	$144.57	$144.55	$144.60
Purchase #7	$41.82	9.425%	$45.7615	$45.76	$45.75	$45.80
7 purchase totals =	$1,059.40		$1,138.8646	$1,138.86	$1,138.85	$1,139.10