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	$186.82	9.203%	$204.013	$204.01	$204.00	$204.00
Purchase #2	$169.71	6.463%	$180.6784	$180.68	$180.70	$180.70
Purchase #3	$89.54	3.315%	$92.5083	$92.51	$92.50	$92.50
Purchase #4	$129.71	8.434%	$140.6497	$140.65	$140.65	$140.60
Purchase #5	$19.87	4.568%	$20.7777	$20.78	$20.80	$20.80
Purchase #6	$184.40	3.869%	$191.5344	$191.53	$191.55	$191.50
Purchase #7	$247.99	3.443%	$256.5283	$256.53	$256.55	$256.50
7 purchase totals =	$1,028.04		$1,086.6898	$1,086.69	$1,086.75	$1,086.60