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	$18.45	9.535%	$20.2092	$20.21	$20.20	$20.20
Purchase #2	$31.72	3.788%	$32.9216	$32.92	$32.90	$32.90
Purchase #3	$64.43	12.463%	$72.4599	$72.46	$72.45	$72.50
Purchase #4	$89.36	8.305%	$96.7813	$96.78	$96.80	$96.80
Purchase #5	$191.99	13.200%	$217.3327	$217.33	$217.35	$217.30
Purchase #6	$13.77	12.393%	$15.4765	$15.48	$15.50	$15.50
Purchase #7	$248.74	8.465%	$269.7958	$269.80	$269.80	$269.80
7 purchase totals =	$658.46		$724.9770	$724.98	$725.00	$725.00