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	$202.26	4.789%	$211.9462	$211.95	$211.95	$211.90
Purchase #2	$86.38	3.429%	$89.342	$89.34	$89.35	$89.30
Purchase #3	$81.25	9.601%	$89.0508	$89.05	$89.05	$89.10
Purchase #4	$48.30	12.303%	$54.2423	$54.24	$54.25	$54.20
Purchase #5	$20.28	7.515%	$21.804	$21.80	$21.80	$21.80
Purchase #6	$198.39	4.864%	$208.0397	$208.04	$208.05	$208.00
Purchase #7	$147.96	4.265%	$154.2705	$154.27	$154.25	$154.30
7 purchase totals =	$784.82		$828.6955	$828.69	$828.70	$828.60