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	$188.91	5.845%	$199.9518	$199.95	$199.95	$200.00
Purchase #2	$110.73	4.826%	$116.0738	$116.07	$116.05	$116.10
Purchase #3	$224.77	9.809%	$246.8177	$246.82	$246.80	$246.80
Purchase #4	$198.88	13.242%	$225.2157	$225.22	$225.20	$225.20
Purchase #5	$67.81	6.566%	$72.2624	$72.26	$72.25	$72.30
Purchase #6	$38.71	9.461%	$42.3724	$42.37	$42.35	$42.40
Purchase #7	$242.67	9.153%	$264.8816	$264.88	$264.90	$264.90
7 purchase totals =	$1,072.48		$1,167.5754	$1,167.57	$1,167.50	$1,167.70