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	$12.72	4.117%	$13.2437	$13.24	$13.25	$13.20
Purchase #2	$186.46	10.211%	$205.4994	$205.50	$205.50	$205.50
Purchase #3	$196.54	9.867%	$215.9326	$215.93	$215.95	$215.90
Purchase #4	$168.31	6.414%	$179.1054	$179.11	$179.10	$179.10
Purchase #5	$105.26	8.175%	$113.865	$113.87	$113.85	$113.90
Purchase #6	$116.98	5.618%	$123.5519	$123.55	$123.55	$123.60
Purchase #7	$97.55	13.139%	$110.3671	$110.37	$110.35	$110.40
7 purchase totals =	$883.82		$961.5651	$961.57	$961.55	$961.60