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	$93.34	12.869%	$105.3519	$105.35	$105.35	$105.40
Purchase #2	$30.67	3.264%	$31.6711	$31.67	$31.65	$31.70
Purchase #3	$109.68	3.378%	$113.385	$113.39	$113.40	$113.40
Purchase #4	$183.88	6.626%	$196.0639	$196.06	$196.05	$196.10
Purchase #5	$123.36	10.665%	$136.5163	$136.52	$136.50	$136.50
Purchase #6	$109.41	12.587%	$123.1814	$123.18	$123.20	$123.20
Purchase #7	$86.29	12.564%	$97.1315	$97.13	$97.15	$97.10
7 purchase totals =	$736.63		$803.3011	$803.30	$803.30	$803.40