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	$41.88	3.811%	$43.476	$43.48	$43.50	$43.50
Purchase #2	$98.92	6.579%	$105.4279	$105.43	$105.45	$105.40
Purchase #3	$93.94	8.835%	$102.2396	$102.24	$102.25	$102.20
Purchase #4	$194.88	9.127%	$212.6667	$212.67	$212.65	$212.70
Purchase #5	$91.48	10.233%	$100.8411	$100.84	$100.85	$100.80
Purchase #6	$249.63	7.732%	$268.9314	$268.93	$268.95	$268.90
Purchase #7	$48.28	10.309%	$53.2572	$53.26	$53.25	$53.30
7 purchase totals =	$819.01		$886.8399	$886.85	$886.90	$886.80