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	$57.61	8.417%	$62.459	$62.46	$62.45	$62.50
Purchase #2	$17.65	4.582%	$18.4587	$18.46	$18.45	$18.50
Purchase #3	$155.80	8.817%	$169.5369	$169.54	$169.55	$169.50
Purchase #4	$41.94	10.872%	$46.4997	$46.50	$46.50	$46.50
Purchase #5	$56.72	9.331%	$62.0125	$62.01	$62.00	$62.00
Purchase #6	$46.68	11.306%	$51.9576	$51.96	$51.95	$52.00
Purchase #7	$82.76	5.609%	$87.402	$87.40	$87.40	$87.40
7 purchase totals =	$459.16		$498.3264	$498.33	$498.30	$498.40