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	$187.46	4.617%	$196.115	$196.12	$196.10	$196.10
Purchase #2	$116.70	3.268%	$120.5138	$120.51	$120.50	$120.50
Purchase #3	$201.42	5.739%	$212.9795	$212.98	$213.00	$213.00
Purchase #4	$34.36	8.534%	$37.2923	$37.29	$37.30	$37.30
Purchase #5	$43.71	3.660%	$45.3098	$45.31	$45.30	$45.30
Purchase #6	$191.45	11.168%	$212.8311	$212.83	$212.85	$212.80
Purchase #7	$162.71	11.693%	$181.7357	$181.74	$181.75	$181.70
7 purchase totals =	$937.81		$1,006.7772	$1,006.78	$1,006.80	$1,006.70