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	$181.93	4.106%	$189.4	$189.40	$189.40	$189.40
Purchase #2	$187.76	6.711%	$200.3606	$200.36	$200.35	$200.40
Purchase #3	$32.75	4.550%	$34.2401	$34.24	$34.25	$34.20
Purchase #4	$110.78	9.699%	$121.5246	$121.52	$121.50	$121.50
Purchase #5	$201.93	3.851%	$209.7063	$209.71	$209.70	$209.70
Purchase #6	$150.93	6.321%	$160.4703	$160.47	$160.45	$160.50
Purchase #7	$94.26	6.504%	$100.3907	$100.39	$100.40	$100.40
7 purchase totals =	$960.34		$1,016.0926	$1,016.09	$1,016.05	$1,016.10