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	$155.33	9.118%	$169.493	$169.49	$169.50	$169.50
Purchase #2	$215.50	4.453%	$225.0962	$225.10	$225.10	$225.10
Purchase #3	$209.83	10.493%	$231.8475	$231.85	$231.85	$231.80
Purchase #4	$67.61	11.864%	$75.6313	$75.63	$75.65	$75.60
Purchase #5	$124.95	7.656%	$134.5162	$134.52	$134.50	$134.50
Purchase #6	$145.37	5.172%	$152.8885	$152.89	$152.90	$152.90
Purchase #7	$169.70	7.429%	$182.307	$182.31	$182.30	$182.30
7 purchase totals =	$1,088.29		$1,171.7797	$1,171.79	$1,171.80	$1,171.70